It feels important to start where I left off. A month ago I looked out over Rainham Marshes with some trepidation. I'd almost resolved to carry on walking that day - to push on the few more miles to Purfleet. As I stood in much the same spot, I knew I'd never have made it if I'd tried. It was a hazily warm morning, sky like silver and slate, the marsh grass reflecting back none of its colour. I made a guess at the spot where I'd discarded my parents' key and paid a silent tribute. I realised with some dismay that I was now linked to this spot forever. My usual memory raid, in and out of a place before it could properly get under my skin, wouldn't work here. In fairness it hadn't worked much as I'd progressed into the east - and from the dirty chasm of Aldgate to the empty flood plains of Dagenham, I'd connected curiously easily with the terrain despite it being so far from my own experience. It was good to be back out here, contemplating a trudge across the gloomy marshes to the river. As I'd made the journey out from Fenchurch Street I'd doubted my ability to get quite as far as I planned today - I felt distinctly post-viral, a sweaty brow and a chest which fluttered oddly, causing fleeting thoughts of mortality and frequent checks of my heart rate. I brushed them aside with a likely unwise bacon roll washed down with more caffeine and focused on the walk ahead.

The first section of my walk felt true to the spirit and purpose of this unhinged enterprise as I strode out along a narrow strip of paved path between deep marsh grasses towards the A13, marching on elegant but strangely ominous stilts across the wetlands. The wind carried the sound away, and the traffic both looked and felt impossibly far-off, like a Patrick Keiller long shot of the viaduct. The road was just about the only thing providing some sort of form in this unsettling landscape, beyond that the land rose into an entirely artificial hill of accumulated landfill. The detritus of London brought to the fringe of the city to decay - safely distant from rate-paying habitation. I realise that I'm alone. I left the last of the dog walkers loitering suspiciously where the path which leads out to the viaduct parted from the local circuit of pale pink shit-sacks and suspiciously steaming tufts of grass. They stood around, fingers flicking over illuminated 'phone screens without clear purpose. Now there is just me out here. Me and cows. By far my least favourite animal - admirable from afar for their sheer improbability, their huge frames suspended from near-exposed spines while they lumber around a field of sub-standard marsh grass, nosing for the long depleted good stuff. The path headed directly towards the river, running parallel to a range of industrial buildings of uncertain purpose - only the last of them giving away its identity as a manufacturer of pre-cooked rice. The hill of waste was between me and the river, and it wasn't immediately obvious how I'd cross it. I soon found myself on Coldharbour Lane, a branch of the Ferry Lane Industrial Area - the wind-blasted, dusty thoroughfare I'd left at the end of last months' walk. The lane wound its way under the A13 and out to the fringe of the waste facility, before becoming this disconcertingly straight service road. Signs barked prohibition. The footpath was sequestered on the southern edge, a concession to the signposted walking routes which inconveniently bisect the trashlands, making them public when they are built to conceal. There was no traffic to beware of. A gatehouse up ahead seemed inactive, the barrier waving lazily in the wind. Just before the public/private boundary, a turning to my right took me along a rising, curved road which followed the outlet of the watercourse, the rice factory on its other bank. As the road rose, there was something about the flat, white sky which gave away the river's presence. A few more steps and the sweep of the Thames was revealed to me. To my right, the towers of the Isle of Dogs shimmered in the distance, while across the water minor industry struggled on on the fringes of Erith. But I was drawn to the east: the high towers of the elegant Dartford Crossing blinking back as it lurched over the river, the towers of the Proctor and Gamble works - it all looked so impossibly far away just now.

The car park was surprisingly busy: cab sleepers, dog walkers and bird watchers with flasks of steaming tea. Those who were awake looked resolutely out across the river. There was a faint sense of loss about the place. With the impressive expanse of the marshes hidden behind the vast mound of refuse, the path was the only escape. I felt almost guilty for feeling so surprisingly energised by the place. The ribbon of silver river called - this project so far had kept me away from water, my encounters with rivers were fleeting crossings at best. Immediately after I'd slipped through the gate onto the path I encountered a warning about straying into the waste lands. Beyond this, the path curved to navigate an inlet, and scattered within it were the hulks of concrete barges, abandoned unceremoniously after wartime service. The mossy, weed-draped hulls emerged from the inlet at crazy angles: some tipped their prows to the sky, others turned their shell-crusted flanks to the path. The forlorn scene was completed by a sculpture - John Kaufman's "The Diver: Regeneration". A strange wireframe figure, emerging from the mudflats, draped in weed and litter. A tribute to those who have worked the hostile estuarial environments out here, covered in the flotsam which keeps this an officially sanctioned danger zone.

The path hugged the river bank as I turned east again, and faced the estuary. The path was, predictably deserted here. Sandwiched between the silted fringe of the river and the fence of the waste facility, my walk was almost a textbook edgeland excursion. On one had I had the silver sheet of the Thames and the curious riparian foliage, on the other a dusty extension of Coldharbour Lane which thundered with heavy tractor units. WIthout their trailing loads, the cabs leered oddly forwards, imbalanced and purposeful, as they hammered around the corner and onto the edge of the plant. One thing both river and land had in common was rubbish. The wind-tossed overtoppings from the plant strung itself through the dried weedstems. Tucked between two tufts of grey-yellow grass I spied a fading nautical chart of the Thames, just out of my reach. An experimental energy generation plant belched out dark, organic sludge beside the road and generated the most curious smell: a sort of sweet, greasy earth, tinged with decay. After crossing a jetty serving the refuse station, I rounded Coldharbour Point and got a view of the territory ahead. Traffic on the bridge flickered in the middle distance, while across the river the waterfront of Erith dominated the view - a collection of modern apartments mimicking the traditional cliff of stucco-covered seafront buildings. Here I turned briefly inland, navigating the path as it climbed around the eastern edge of the waste mound. Rainham Marshes stretched before me - the A13 and High Speed 1 grazing the edge of the vision on low viaducts, which alternately rose and fell to cross each other just out of shot. Beyond the road, the village of Wennington and a smudge of red which signified the brick buildings of Purfleet. Between me and the distance? Nothing. An expanse of wet scrubland, marsh grass, ditches cut deep into the soil. Occasional human trappings were becoming integrated - rifle targets slowly discolouring to match the earth, bird-watching hides gradually becoming hidden themselves. The view from the slight elevation of the bund which protects the marsh was oddly spectacular and affecting. Looking back across the river, the flat and open foreshore was equally evident, emphasising the height of Dartford Creek Barrier which towered over the mouth of the River Darrent where it emptied into the Thames.

I spent quite a while chatting and lingering in the RSPB centre on the edge of the marsh, a curious half-glass camouflage block which couples a tea room and public facilities with a relatively luxurious hide for the discerning twitcher. The coffee was passable and the locals were interesting, if not terribly well informed about the river path. After being passed among a number of them, they proved knowledgeable enough about the route back towards London but they remained remarkably hazy on the eastward path. They knew I could get into Purfleet, but after that? Who knows. And to Southend! Why? It occurred to me here that they had me down as a more traditional kind of walker than perhaps I really am, and that they'd have seen landfill or a reeking soapworks as a barrier to passage. Not so far me of course, so I'd have to trust my nose. I left the impressive centre and set off over the bridge into Purfleet, passing the historic village green and the Powder Magazine - a survival from 1759. The river path dwindled to an access-only route to the inevitable stacks of river-front apartments, so I turned inland and found myself walking a surprisingly busy road through the bleak remains of the town. My first call was St. Stephen's Church - a long, low and fairly modern building which served as a chapel and church hall for the long-demolished Purfleet House. The assumed history here though is entirely myth - this was likely the model for Carfax, the house scouted by Jonathan Harker for Count Dracula. It seems a forlorn enough spot - but that has more to do with Purfleet's down-at-heel aspect than any supernatural force. Near the level crossing a single corner shop was open, its bored owner reading the classified ads at the back of a local paper with impressive focus. Anything to make time pass just a little faster out here. I bought water and chocolate and set off again. The station was oddly inviting - a near immediate escape from this odd little place which seemed to be almost entirely asleep on a Saturday afternoon. A bus sputtered by, picking up speed after a stop on route to Lakeside, the windows misted. Full of eager shoppers being drawn into the retail epicentre. I crossed the street, hedging my bets on which pavement would fail me first, and headed out of town. The road leading away from Purfleet is nestled at the foot of a chalky cliff, with new housing developments stacked against it and rising to meet it. Between the road and the river is a widening band of industrial land - including the vast oil terminal I was passing, realising I had a family link of sorts with the area. I didn't stop to investigate - navigating the cars parked on pavements, and choosing the right moment to slalom around them, avoiding the oncoming stream of tankers was something of a preoccupation. As I left the built-up area behind, I spotted the unlikely bulk of the Royal Opera House production facility in a large hangar behind a development of neat, new housing. It was incongruous and strange, but perhaps no more so than the continued existence of places like Purfleet at all. These edgeland towns which have been reduced to near hamlet status by virtue of the gravitational pull of nearby out-of-town developments seem improbable at best, and likely unsustainable. I wouldn't be surprised if I came back to find I'd dreamed Purfleet, written it forward from fiction and believed my own overcooked prose.

The official exit to Purfleet appears to be the strange dog-leg junction with the A1090. Suddenly, the environment is full of stimuli which have been absent in the village. The sky opens. The slender towers of the QEII bridge loom suddenly large, the oversized pylons carrying power cables across the estuary nestled behind them. HS1 crosses the road too, plotting its course to head under the river not far from here. Trains don't so much rattle as blast by, leaving a dusty gust of air in their wake. I take the exit for Thurrock here, feeling suddenly a long way from where I set out in the cool green calm of the marshes, but equally far from my goal. I'm almost disheartened here as I walk through rough scrubland, with a curtain of trees between the road and the plain of warehouses and refineries. But the bridge is upon me now: towering ominously above my route, a lattice of road and railway rising and plunging across the road. Passing underneath is unremarkable, and pushes me unpleasantly close to the thundering fuel tankers. I can feel the motorway above more than I can hear it. I feel my jawbone vibrating, my teeth touching in rhythm with the traffic above. The air is gritty with dust thrown up from the road, and cast down from the bridge - I feel it crunching between my teeth. The red ensign of the Ibis Hotel forms through the haze. I realise I've crossed another margin here: I'm outside the M25 now. London is definitely behind me, a punctured balloon which I'm escaping from in slow motion. This is a parody of the greenbelt - a rustbelt, industry not economically tolerated within the ring of concrete slowly decays here. Even the Waste Transfer Station had more purpose, more cachet than some of the cut-price tyre merchants here. Passing the Ibis is payment of homage to an unlikely literary landmark: much of the action of Iain Sinclair's "Dining On Stones" focuses on the hotel. It is a watchtower above the road, a proxy for the sublime tracking shot Chris Petit pulled off in Bristol for "Radio On". Sinclair's characters - often simulacra of himself - look up at the blank, reflective windows, or down at the equally impossible to read motorway junction. I try to look beyond the hotel to the sign gantries and wonder if it was here that Jack Whomes, brother of convicted Rettenden Murder John staged his traffic-stopping protest? This spot, where roads meet and join to form the last crossing of the Thames, is marked. It's a here-or-nowhere moment. A final opportunity to cross the water or remain on the north bank all the way to the coast. A crossroads of last chances. As a pedestrian though, I'm condemned to remain.

West Thurrock is a marginally energised take on Purfleet. A long string of communities, differentiated only by custom and local knowledge. Essentially the road is a long terrace, punctuated by views through to the riverside industry, which looms large over the Victorian homes. My feet are starting to drag, and a detour into the industrial zone to find the tiny church of St. Clement, eclipsed by the soap factory, just isn't practical today. As I cross the unmarked boundary of South Stifford, the unmistakable waft of skunk permeates the air. A front door bursts open, and the lazy Saturday afternoon drone of traffic is suddenly interrupted by a volley of barks. A squat, balding character weighed down by heavy links of plated chain swaggers into the path with a fistful of dog leads. Ahead of him, a pack of short-legged, bull-nosed terriers slaver and skitter, blinking in the light and scuffling for freedom. He presses a phone to his ear and yells into it. I wonder how I'm going to write this into my journey without pressing all the stereotype alarms? A group of Burberry clad young guys head out from a side-street and knock a nearby door which pulses with low-frequency reggae. No-one answers so they slink off, laughing and kicking each other from behind. I feel like I'm in a cartoon of Essex. All the mis-spelled sign boards of Dagenham, the mock-country pubs of Barking, all the things I could edit out of the Essex I'd experienced - and all of the liminal spaces and curious corners I could highlight in their places! But now this blew my cover. In the gravity of Lakeside, the gusting litter reflects its franchised restaurant chains rather than the line of local chicken take-aways. I'm an imposter here. I'm not spending any money.

I realise that I'm arriving in Grays. There's no sign or specific moment of transition - this road feels endless, though I've begun to wonder if I'm inexplicably looping by the same few terraces, the same tired little newsagents? The only real signifier is the change in the roadsigns - Southend is now a destination. Out of the gravity of London, beyond the skin of the Orbital Motorway, it is again acceptable to refer to regional destinations. I'm fooled into thinking the end of the line is nearer than it has seemed for most of today, and I'm spurred into a final push. I don't really get into the Town Centre, skirting the edge towards the station and seeing the square, modernist tower of the State Cinema glowering over the bus station. I'm tired - so tired I misread the station completely - heading for the bay platform with an infrequent service via the route I've travelled today. I realise there is a train soon via South Ockendon, but it's on the other platform. I stumble idiotically around looking for a way to cross, before finding the dank subway just as I'm about to give up and wait for the next train from the bay. I'm not sorry to escape Grays, even with the Lakeside-bound hordes sharing my train. It's been a long, tiring and dusty day which has already left me feeling confused and curious to research these odd surroundings. I'll need to come back here to pick up this route at some point, but I'm a little afraid of straying out into the open country of Essex. The rural gothic of the mysterious east beckons, with its freight of folk tales ancient and modern.

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

So far it had been a very civilised weekend. It started a day early, with an early Friday morning dash to Crewe in order to meet the positioning move. There was a little frustration as a lack of reserved seating and some fairly anti-social railtour passengers meant that things got a little fractious. However, it was soon sorted, and I was able to enjoy the run down the West Coast Main Line into Euston. The weather was fine, and I broke my walk to the hotel to enjoy coffee in an old haunt near Kings Cross. The walk to my digs for the weekend took me to the heart of Clerkenwell and the edge of Bloomsbury - and it was both good to be back and frightening to grasp the pace of change here on the edge of the City. I retraced my steps early this morning - the tour didn't in fact leave until 08:18 - a very civilised hour for such things - but there is something special about wandering around London on a chilly but bright spring morning which I've missed. Lots more coffee too, before assembling with the usual crowd inside a chaotic Kings Cross. The renewal work here has made the place confusing and difficult to use - but it still functions, and soon after having managed breakfast and coffee, 57601 hummed into view with the stock. A piper - a genuine Royal Scots Grey I'm told - struck up, and things were underway. This was going to be a little bit special...

The premise was a simple but emotionally charged one: its fifty years since Deltics were introduced, and thirty since they were retired from service on the East Coast Main Line with HSTs taking on their duties. This still seems to cause some chagrin among the older enthusiasts - but there's always a question for me about whether the HST would even exist without the Deltic - a proving ground for the concept of sustained high speed diesel running. In any case, 55022 had been spruced up for her 50th - a fresh coat of paint, bringing her into the livery she was sporting on her last runs on special trains. The job had been done beautifully, with grills and pipework picked out in silver, and the engine sparkling. Things began as they were due to continue - a fast departure and some thunderous running north. Then the sun appeared too, even the weather seeming to sense the occasion!

So, 55022 did exactly what she was designed for - she sped along the traditional route (changed of course only at Selby and Penmanshiel) managing what are reported to be some quite considerable speeds. There were no diversions up curious branches or routings via less-trodden byways today. Delayed slightly at Grantham we passed Pathfinder's Norwich-bound charter with a pair of Class 20's and a 37. Normally I'd have been torn, but not today. Underway again we soon made up time and arrived in Edinburgh on the button. Another piper greeted us, along with some former regimental colleagues of Royal Scots Grey, who collected funds and chatted with the crowds happily.

With the stock off to Craigentinny for a run around, grabbed some lunch and wandered around the always busy and interesting Waverley station. Chatted to folks from the tour a little and met a fellow blogger. Before long the stock was heading back into platform 19, and we were ready for departure southwards. If anything, the return run was even more impressive than the outward. Long periods of sustained very high speed running, despite a switch to the slow lines south of Peterborough. We were consistently early, and it seems who ever was playing trains in East Coast control today was a Deltic fan, as we were allowed to depart swiftly. Thus we ended up keeping pace with the 'real railway' admirably, and it was tempting to imagine what would have happened if perhaps the Deltic's hadn't been taken out of service thirty years ago?

Arrival back at the Cross was an impressive fifteen minutes early, on admittedly the usually slack railtour timings. The sense of occasion in the crowds milling around the engine was palpable. Even the notoriously impassive and enthusiast-unfriendly staff were sneaking out their 'phones for a picture of the gleaming workhorse which had just marked a bittersweet anniversary. As for 55022, well she'd done what she used to do every day - and made it look like it was still an every day occurrence.

A very special day on the railway - which reminds me why I got involved in the first place.

Today was the first day I've felt almost normal, so I decided it should be the day for one of my pointless but entertaining epic dashes to get mileage and new track. After haggling over a Portsmouth ticket yesterday, and coming away with a rather expensive but completely unrestricted one, I set out on the 0628 for Bristol expecting a long day.

Pleasant enough ride down to Portsmouth. Last visit I went straight to the Harbour for the ferry crossing, so this time I hopped off at Portsmouth & Southsea and explored a little around the station, which is an unusual split-level half terminus and half through station affair.

Next leg was a run up to London Waterloo via Petersfield on what turned out to be a 5WES unit. I'd forgotten how comfortable these were, and despite being based on the Mk3 coach design, how much better they'd turned out. It was also somewhere on this journey that I decided that I could get back to Portsmouth by another route later... But doing another route home meant missing out on the planned London to Guildford via Effingham Junction leg. So, on arrival at Waterloo I threw caution to the wind and made an absurd double-back to Guildford, staying for only a quick coffee and a brief potter around the station environs.

Returned to Waterloo and crossed London under a threatening bruise-like sky. Spent some time exploring and people-watching at Victoria, one of the terminii I use little - so it retains the mystery of the 'big London station' in my imagination. Wondered if I'd get 377s back, but instead got (what I think was) a 4VEP and a 4VOP. Southern units confuse me - I'm learning, and will no doubt have it sorted in time for the complete withdrawl of slam-door stock. Granted, at current rates that could give me some years however!

So, left via Gatwick and Three Bridges on a Portsmouth/Bognor Regis train, which divided at Barnham. Now, this happens all day every day, but I really felt the pain of the South Central staff - offering repeated, detailed explanations of where people should be on the train, but still finding people in the wrong place, or just plain ignoring them! Arrived back in Portsmouth in good time for the 1724 to Bristol. Now the fun starts. It was solidly packed most of the way, and despite starting on time, leaked minutes for no reason at all! By Trowbridge we'd just stopped. Later heard that someone had been taken ill on the platform and the train preceding us had stayed until medics arrived. More delays due to lost paths near Bristol brought us in 41 late by my reckoning.

Still, I set out for an epic day, and fifteen hours of travelling later I arrived back, tired but happy enough. I've never quite been able to explain why I do this kind of thing - best guess is that it's the nice, safe suburban version of explorers who get themselves lost to see if they can get home!

An industrious and productive day. Finally persuaded ./configure to check for wvdial in the Gtkdial build process. Fixed some minor 0.3 bugs, installed the latest translations, and I think I'm about to package up a development release. Also learned a bit about consolehelper which will prevent lusers from playing with the new (and still immensely broken) editor component. Finally got Evolution built, after a nightmare trying to compile OpenLDAP 2.0.7.