It had been a challenging few weeks - the seasonal sickness that descends on all those condemned to office life had struck and left us tired and exasperated. To cap this, of all the body parts which could choose to exact sympathetic rebellion, my right foot was painful. I'd spent the last week of spasmodic coughing and sneezing poring over maps of Essex and I just couldn't find an easy way of advancing along the A13 - the walk was either too short to be interesting, or far too long for my current condition. Meanwhile, the day crept up on me strangely quickly. Rather unexpectedly though, a reserve plan sprang into being. I'm not sure how, or why I found myself idly looking over the OS Map of the Lee Valley - but it struck me it was time to return to the river I'd spent so much time mythologising over the last few years. I planned hastily: I'd walk into London rather than out, taking advantage of the parallel railways which flank the Lea Valley to make my escape if my range was limited by fatigue or foot-rot, and I'd start outside the M25. It made for a good long walk which symbolically cut another axis into that great circuit. The day dawned surprisingly fortuitously for a walk. The weather was perfect for walking, with blue skies flecked with cloud and a cool breeze. My foot too, appeared to have relented and healed somewhat. I tested my boots and found that they were far more comfortable than regular footwear had been. The journey to London was a relaxing, quiet pause - the first in a few busy weeks and I stalked off for the tube at Paddington in good spirits. A quick spin around the Circle to Liverpool Street, and then armed with coffee, onto a suburban service out into Hertfordshire. Rebranded as TfL Rail, the Overground Orange motif spattered across the decor, with a freight of spaced out kids nodding and sputtering home from a Friday night in the clubs. Over the rooftops of Bethnal Green and Hackney, then into the strange suburban hinterland which breaks like a spent wave on the western side of the Lea Valley. The Turkey Brook, passing under the line deep below signalled that it was almost time to alight, and to begin walking.

I was briefly disoriented on exiting the station - blinking at my map in the sunshine, I soon spied Trinity Lane heading off between ranks of suburban houses. The lure of possible supplies on the High Street was strong, but I had the urge to start walking. The surprisingly warm morning was wearing on, and I was still a little concerned about my walking speed and endurance despite having a pretty solid escape plan. In truth I didn't want to have to abandon a walk - it just wouldn't feel right. Immediately on entering the lane I realised I was walking a watercourse already. Sandwiched between the houses on my right and the road was a deep ditch, bridged by driveways into the pleasant looking suburban dwellings. Theobald's Brook, having emerged from under the road junction at the station, was leading me to the river. Being hazy on an exact route, I decided to follow Trinity Lane into the Lee Valley Country Park with the brook as my guide. Eventually the road dwindled to a lane leading to a level crossing over the railway from Cheshunt, and after a careful crossing I found myself in the park at last. The brook swerved away to join the Small River Lea, while the path opened into a vast greensward dwarfed by pylons. I recalled being taught as a small boy that electricity and water don't mix well - but here in the Lea Valley they are constant companions. Pressing on into the park I crossed the Lee Navigation near the Lee Valley White Water Centre, complete with its plaques bearing witness to Olympic renewal. The path rose here, with a good view along the quiet, emerald waters of the Navigation. There was a distant hum of traffic and a buzzing of insects. I was back in the valley, and glad to be here.

For a brief spell, I was walking beside the Old River Lee - the slow, stymied and meandering sibling of the Navigation which winds along the western edge of the valley. Shaded by trees, the emerald surface of the water rippled lazily as I approached the road near Waltham Town Lock. I had a choice as I surfaced - to continue on the banks of the river, or take the path beside the Navigation. I chose the western path - essentially because it appeared to involve less diversions around incomplete pathways, less complication - and perhaps less chance of temptation to deviate from my goal. Also, if I made it all the way, I'd be leaving the path at the same point where I parted from the valley over three years ago. It was a symbolic relinking, if nothing else. Immediately on crossing the A121 and descending to the bank, the character of the water changes. Hemmed in by a vacant industrial wharf in the midst of a dusty clearance process, the water is slick and dark. Stretching south, butting against the straight line of the Navigation are a range of warehouses with 'excellent motorway links' and claiming journey times of an hour to Heathrow. For the first time today I feel almost uncomfortably hemmed in by water - I sense the Small Lea lurking to the west, and only a narrow spit divides the Lea and the navigable channel here. Trees hang listlessly between them, and the surface shimmers with chemical rainbows and a faint heat haze. I'm suddenly reminded of The Waste Land:

The river sweats oil and tar

But the walk is pleasant. I'm not really hitting my usual pace - I'm just enjoying the cool of the river breeze and the sun on my face. It feels like a long time since I walked in sunshine. The rivers stay close here, as the shudder of motorway traffic begins to make itself heard. There is no great ceremony here, no arcing bridge. Instead a low, concrete bridge spans the collected rivers, the traffic just feet from my face as it shrills by. The road is flowing faster than the water, a lane of large lorries obscuring the sun before I reach the bridge. It's cool in the shade, and the slope under the pillars opens into a muddy lake of litter. A recently dumped, not yet torched Peugeot 206 awaits its fate beside a pile of clothes and soft-furnishings. It is surprisingly intact, and appears to have been driven here. The thought of off-roading across the marshes is absurd. Beyond the plain of waste, I spot a gateway leading up a rise and away from the river. I'm reluctant to leave the path - but I'm drawn to the light after being under the bridge. It's a slick, grassy scramble up the muddy slope on the edge of Rammey Marsh with just occasional tufts of coarse grass to aim a boot at - but I'm rewarded with a chance to be at close quarters with the M25 in a way I'd never quite expected. A huge Variable Message Sign curves over the carriageway nearby, and a bold blue board marks the border in capital fashion: HERTFORDSHIRE. As traffic shudders by, little more than pale streaks of colour and rushes of air, the infrastructure broods silently. The scale of the bridge, the towering pylons forming a lattice of wires across the road, the massive hulk of the signs - it is strangely awe-inspiring up close, out of the mediated frame of a windscreen. I paused here for quite a while, just watching the road while contrails crossed the sky. Here - for perhaps the only time on my walk - water wasn't the dominant force.

Scrambling back down the bank was more complicated and less dignified than the ascent, but I was soon back on the path and heading south. The river runs in three channels here - the Navigation and Diversion parting to envelop Enfield Island Village, with the Cattlegate Flood Relief Channel skirting the eastern fringes of the valley. I confess to being lost in the terminology here - ill-prepared for the complexities of the waterways I'm trying my best just to stay on course. But the lure of refreshment is too strong, and I climb the steps onto the bridge which leads into the former Royal Small Arms Factory. Inside the water-bounded compound it's a mix of old and new - long, low brick buildings which date from the island's former occupation rub gables with new housing stock, built in similar but slightly off-key styles. The overall affect is jarring and oddly creepy. There are few people around until I get to the tiny and ill-organised Tesco Express store - the only amenity here which is in business. I head back to the river with my purchases in hand. It's dusty and dry here, work still going on to build more housing on the southern edge of the site. I recall the tales of toxic dust when the main area was upturned and built on, and I try not to breathe until I'm safely in the shade of Swan and Pike Pool. I rest beside the water while across the cluttered, dirty pond someone does yoga silently. It feels calm and restful enough here - but that seems such an unlikely pursuit so close to the heavily polluted motorway air.

The valley changes character as I set off again. Turning south where the huge Enfield Energy plant dominates the view, the Navigation is a broad, straight canal. Right away we're joined from the west by a confluence of the Small Lea and the Turkey Brook, running in at a reedy, inauspicious junction. The Navigation's other sister streams have parted from us, running along the eastern edge of the valley and now separated by the vast hourglass-shaped expanse of the Chingford Reservoirs. The most northerly is the King George's Reservoir, with steeply raked grass banks separating countless millions of gallons of water from the rivers. This was, until 1951 an aerodrome. This flat, empty situation on the valley floor proved perfect for these experiments in watering a vast urban metropolis. A similar undertaking would almost never succeed now, risking strangulation by the twin hands of planning regulation and protest movement. The challenge of holding back such vast volumes without slippage and disaster resulted in a long-standing British dominance of the soil dynamics field. The towpath continues, skirting the minor kinks in the southerly course of the Navigation. An overflow channel leaves the canal, a concrete culvert full of mud and silt, hugging the perimeter of the artificial lake as a causeway carrying the A110 separates it from the William Girling Reservoir. The causeway is a passage from pub to pub - from Nags Head Road to Kings Head Hill, taverns celebrated along a route marking one of the few horizontal crossings of the odd, somewhat beleaguered valley. This lake - named for the chairman of the Metropolitan Water Board at the time of inauguration - is more elegantly tapered than its northern counterpart, the southern reaches pinched by the rising flanks of land which support Chingford and Tottenham. Looking west, a rank of four tower blocks at Ponders End dominate the horizon, rudely emphasised by the empty industrial lots between the river and the housing estates of Brimsdown and Edmonton. South of here, the western bank is dominated by the Lee Valley Athletics Centre - a pale shadow of what was meant to be the pre-Olympic dream: a revitalisation of the valley through sport has always been the officially preferred mechanism. At Pickett's Lock a crumbling boathouse is sheltering three preening swans, the plans for the 2005 World Athletic Championships long forgotten and eclipsed by the great events of 2012. The embarrassment of earmarking a site which was too difficult to reach and too expensive to develop is almost erased by later profligacy, by a project just too big to fail. There is a golf course now, man-made lakes, a sports centre to replace the original Pickett's Lock centre. But thankfully the river still runs undisturbed. The sun is riding high now and my forehead is starting to sting where I'm sweating. I fear I may be turning pink. I see virtually no-one on the path now except for the river-dwellers working on their boats and the occasional jogger. Most sane Englishmen are safely indoors, even though the April sun lacks the power of summer. I walk on.

Almost hypnotised by the long, yellow stone path stretching ahead, I'm surprised to hear the sound of traffic returning. The path opens into a vast stone chamber under the junction where the North Circular meets the Ravenside Retail Park. The complex web of slip-roads spans the entire valley, with a roundabout dominating the dormant space between the Lea and its navigable stream. As I pass under I instinctively turn to photograph daylight above me, penned in between the carriageways. I press the shutter as two huge birds spread their wings and head for the sky between the slip roads. Meanwhile a rowing boat filled with laughing Sea Cadets lurches and splashes under the A406. I'm inside the City's inner road necklace now - and any sense of rurality disappears. The walkway is narrow, a metal crash-barrier separating it from the dusty, unadopted mess of Towpath Road - existing only to serve a complicated jumble of businesses and the Arriva Edmonton Bus Depot, forced into the dwindling neck of land between the rivers. Dust rises from the passing buses, obscuring what appears to be an illicit trade in waste white goods. I'm pressed against the barrier for fear of cyclists who don't ring bells here. Thankfully, the River Lea soon rejoins and I'm on a thin spit of land between two wide, slow streams of water. The rank of pylons which have shadowed my route here from Waltham Cross have split, flanking the channel on both sides, placing me in an eerie procession. A genuinely electric avenue. A glance at the map shows an explosion of water here - the bulging circle of Banbury Reservoir is the last of the Chingford Chain, with the Walthamstow waters taking over the valley. I'll see less of these - they favour the eastern side of the Lea Valley, with only the Lockwood Reservoir sidling up against the River before I leave the valley.

This last stretch is hard going. It's been a hotter, slower walk than I'd expected and despite being mesmerised by the strange vistas of the valley, I'm tiring. A curving footbridge gives access to Tottenham Marshes and a series of well-used green links along the edge of Pymmes Brook. The afternoon is cooling a little, but the sun remains high - and couples push strollers and wander the path. The eastern bank is quieter until Stonebridge Lock where the only option is to cross the gates and join civilisation. The former café and toilet block is a focus for walkers - a place to reevaluate their limited post-prandial stamina and turn back before it's too late. Before they are walking the valley like me. I spot an entire family on a bench near the lock gates, the elder gazing down at the end of his walking stick. When I resurface from using the facilities they have crossed the lock and assumed an identical position on the western bank. My ceremonial guides as I embark on the last leg of my walk for today. The Navigation is busy between here and Tottenham Lock - the waterway filled with boats in various states of repair, from semi-sunken to beautifully decorated, and the footpath busy with walkers and cyclists. An alarmingly drunk man mis-steps toward the water, a passing family oscillating between concern and distaste. When I pass him he's facing inland and fumbling with his flies, smiling blissfully to himself. Saved again by instincts which defy his inebriation.

Despite knowing how close I was to my goal, Tottenham Lock came upon me unexpectedly. The gentle curve of Ferry Lane bridge and the strange oblique sculpture which sits beside it appeared in negative due to the glare of the sun - which now also bounced back at me from a range of tall apartments built since my visit in 2012. Pymmes Brook was now alongside me too - a stinking ditch in a divided concrete chasm, chasing its final few metres before being subsumed into the broader waters of the Lea. At Ferry Lane I resurfaced and crossed the road to survey the spot I'd left the river three summers ago. Aside from the near-completion of the vast development behind me, little enough had changed. But for me - everything had. I'd always anticipated picking up this walk in a northerly direction, heading away from the City and the repellent enforced buoyancy of the Olympic summer. Life took a different turn, and it seemed fitting to be coming back to civilisation, part of something bigger and more human from an entirely different angle. The last few steps to the platform at Tottenham Hale were as painful and frustrating as last time. There is no access to the station from the east, no one walking in from the lakes. It felt strange to be coasting across the wide expanse of green marshland near Clapton, after spending a day surrounded almost entirely by the waters of the Lea Valley and I realised I was catching probably my first glimpse of the familiar city skyline today as I headed back towards Liverpool Street. The wide swathe of water continues, paralleling the railway line - and I know that I'll need to return to walk the eastern reaches if I'm to fully understand this remarkable and confusing place.

You can find a gallery of images from the walk here.

Only weeks after my last jaunt, I find myself trudging London streets early in the morning. This weekend hadn't gone as planned, and with the overnight trip which would have meant saving a night's accomodation postponed, I'd wedged myself into a tiny Travelodge room near Kings Cross once again. No pacing the streets of Clerkenwell this time, as I was sick and tired, nursing an annoying cough which I suspect I picked up somewhere on last week's trip. Sleep had been pretty elusive too in this curious but huge hotel, and I had the joy of a different one tonight as I'd planned to be staying near the tour's set down at Clapham Junction. This meant that I had the entire world stuffed into my rucksack, and it was a pretty grim walk to Euston. However, as I crossed Pentonville Road and looked east, a flaming sunrise peeked over the brow of Penton Mound. Momentarily struck by this, I stood like an idiot on a traffic island appreciating London all over again. Top priority at Euston was to find coffee, and with a sensible margin before the tour started I was able to sit back and relax, waiting for my cough to subside before heading for our train. Bumped into the usual crew on route too.

The premise for the day was a 'Buffer Puffer' style dash around South London, taking a top-and-tailed pair of WCRC Class 37s to places they'd never normally go. We set off up Camden Bank before curving away to the West London Lines at Willesden. From here we turned south again for a second pick-up at Clapham Junction. It became clear here that there was a fair few spare seats on the train, and that our neighbour didn't appreciate the chatter and banter. So we moved back into the end of the next coach where some other reprobates were located. From Clapham, we pressed on through the South London suburbs to East Croydon and then to Caterham for a reversal. I had of course been here before with a loco-hauled train, and on that occasion I'd felt pretty unwell too as it turned out. Put the thought that history might be repeating itself out of my mind, and rejoined the train for the next leg. We retraced our steps into London taking subtly different tracks, and gained the South Western route at Wimbledon. From here we had a somewhat speedier run into Guildford via Effingham Junction. Time here for a photo stop, a round of coffees and a chance to briefly enjoy the pleasant sunshine before hopping back on board for the next leg.

Once underway we had another uninterrupted run, this time into London Waterloo via Leatherhead. With the train covering all of the planned track, and taking in some pretty unusual lines and crossovers for the microgricers on board, spirits were high on arrival in the capital. Feeling pretty grim, and waiting for the medication to kick in, so stayed on board for a catch-up with friends until the whistle, when I took to a drop-light for the crossing of Linford Street Viaduct. I've done this bit of rare and disused Eurostar-related track fairly often in the last few years, but it remains and interesting ride over the mainlines. Once we'd descended onto the Chatham Lines we began to pick up pace on the run out to Tonbridge. With lots of unfamiliar Southern region units flying by, I was urged to stay awake and vigilant by the desperate northern crew! Managed to improve my usual record at least I think. A surprising amount of civil engineering activity in the yard at Tonbridge with a fair number of Class 73s stabled. A reversal here and we were soon headed along the straight and rather dull route to Redhill. We'd been carrying just a few minutes delay after the jaunt through Kent and we soon made it up here, with an early arrival for our next reversal. Time to wander on the platform for the first time in years, and to get some further shots of our train. The remaining legs of the trip weren't rare track as such, but they were extremely rare in terms of loco-hauled trains. Setting off via Three Bridges and Horsham, we were soon dashing through the Arun Valley towards the coast. It was warm and I was sleepy, so my unit spotting became erratic and I was forced to volunteer to buy more coffee, since alcohol was out of the question in my condition. After bemusing the locals waiting at Barnham station, we curved towards the sea and entered the once grand terminus at Bognor Regis. In fairness, the station platforms seem to have had a fair bit of attention and it was clean, tidy and very well-kept - certainly better than my last visit which I note was almost exactly seven years ago! Reversing that days moves, we next headed to Littlehampton where a forty minute break saw the passengers from our train scatter rapidly to chip shop, pub and cashpoint. Given that the town had already entered that post-5pm gloom which afflicts most seaside resorts, I suspect experiences were pretty varied.

Back on board with some provisions, and I was feeling much better than I had all day, but pretty sleepy. Settled down for a pleasant evening run back into London with a little bit of light still in the sky. I've written before about how much I love arriving over the rooftops and looking down into the city streets, and this was just about the perfect evening for this activity. Back on time, the Chesterfield contingent prepared to bail out with me at Clapham Junction to make the train back up north - a fairly tight connection. As we arrived at the bottom of the steps in the subway I sent them skittering off to the taxi rank, while I aimed for the much quieter Grant Road exit and the pleasant and familiar evening walk to the Travelodge at Battersea. Not much had changed there either, and just like before I wrote a mental letter of complaint about all the bits of my room that were broken, missing or unpleasant, before deciding I needed to sleep very badly. Despite my aches, pains and annoying coughing today had been a success - the route, complex and challenging to operate, had worked wonderfully and I'd spent the day catching up with a really decent bunch of people too. Settled down to sleep, safe in the knowledge that, this time at least, I hadn't developed swine flu into the bargain!

To celebrate the 150th anniversary of the beginnings of The London & Middlesex Archaeological Society there are many special events planned - today was the first of a series of 'Central London Walks', this time visiting London Squares. Started early from Weston, with a cool and misty journey diverted via the Berks & Hants route. First to Waterloo Bridge for coffee and breakfast. Met the other walkers on the River Terrace at Somerset House. The walk started in now powerful sunshine, and headed north over Aldwych and the site of Saxon Lundenwic, to Covent Garden. The arcade, part of the extension to the Royal Opera House gives an idea of how the square looked when first built. From here to Inigo Jones curious St. Paul's church with its decorative but ultimately pointless east elevation. West again now, to Leicester Square.

It is this part of the walk I dreaded. I'm not a fan of the gaudy, crowded precincts of the West End of London. A lot has changed however since I last visited. Here Jon Finney, our guide spoke a little about the responsibility of those who conserve or preserve sites, and how doing so can change the nature of a place. Indeed Leicester Square seemed more spacious, personable and open than before. We proceeded to Trafalgar Square via the rather silly Sainsbury Wing of the National Gallery, and I was impressed again by change. Gone is the impossible circuit of traffic, and a wide open prospect down to Whitehall gives fine views. The square is accessible and usable, but as our guide points out - is no longer a square!

Under Admiralty Arch next, along the Mall and past the Nash terraces - seemingly built of pink blancmange. Nash buildings always make more sense to me from a distance, and at close quarters lack any interest at all. Up the steps beside the ICA (and the mysterious doorway which haunts Subterranea Britannica), and to St. James' Square - London's first and at one point most exclusive residential square. Built as a speculative venture, it became a haunt of Dukes and Earls. No residences or indeed original buildings now surround the square. The walk ended at Burlington House - home of the Royal Academy, where a remodelled courtyard works less well. A chance to look around restored William Kent rooms before heading off into the midday sunshine.

This walk took me to areas I tend to avoid - my interest and knowledge of London lies east of here. Decided to capitalise on the opportunity and visit one or two sites which I would normally not get near. Started with a sweep through St. James' Park to Parliament Square, something I did on my first solo visit to London many years ago. Impossibly crowded, so I decided to seek out Westminster Cathedral. I'd been reading about the Cathedral recently, and the failing health of Pope John Paul II had ensured it being featured on televison recently as a backdrop to ecclesiastical vox pops. Problem was, I couldn't find it! It seems not to feature on any map of the area at all. Struck out along Victoria Street, eventually finding a direction sign - soon enough the oddly octagonal, red brick byzantine influenced tower appeared over the rooftops.

On turning into the piazza around Bentley's amazing building I was struck by the odd atmosphere. Satellite broadcasting vans everywhere, cables running to expectant cameras and off-duty newscasters lounging on bollards. People were visibly waiting for the Pope's passing. The only person really doing anything in that strangely quiet square was a Big Issue seller, proclaiming his wares from the Cathedral steps. On a strange whim, went inside. The interior was wonderful. Eric Gill's stations of the cross adorn marbled pillars, whilst overhead is blank brickwork. The usual conspicuously rich iconography of a Catholic place of worship looks less out of place here than in older churches. A small altar with a picture of the pontiff had been set up, and a continuous stream of the faithful visited it, lit a candle and moved on. The Cathedral was filling slowly and silently with people. At one point, a Cathedral official approached a microphone and called for attention - the expectation was palpable. He gave a message for someone to meet their daughter at the main doors, nothing more. An entire congregation let out a sigh of relief. Some in fact, fell to their knees. I sat for quite a while mesmerised by the atmosphere, but eventually felt extremely out of place.

Fled to more certain ground, and found myself pounding my usual beat of Blackfriars, Newgate, Smithfield and Clerkenwell before heading back to Paddington and a quiet journey home. A strange day where I challenged my prejudices in many ways.

Productive day. Early start - shopping. Had no idea how much chisels cost! Borrowed one instead, but did purchase a speculative birthday present. Lots of work throughout the day on the chess board (and I have scars to prove it). Finally finished it at about 7pm but couldn't find anyone around to display it to! Released gtkdial 0.3.5 and announced it everywhere.