Metropolitan Line: Harrow-on-the-Hill - Uxbridge

This one, final branch of the Metropolitan spools out through a chain of pointedly well-kept, purposefully low-key settlements and suburbs.

All of the stations, apart from the terminus, were pretty much deserted when I passed this way. It was late on a Saturday afternoon, and dusk was creeping in. Nobody seemed much gripped by an enthusiasm to travel anywhere local. Groups of teenagers were heading into London for the night; groups of shoppers were heading back home to Uxbridge. In-between, little happened.

This was the last stretch of the Metropolitan to be built, in 1904. Many of its stops weren't added for several years. One didn't materialise for almost two decades. The whole branch has a sparse, uncluttered feel. Nobody travels this way out of pleasure.

West Harrow didn't become a station until nearly 10 years after the line arrived. Unashamedly small, it feels almost apologetic for existing.

Nonetheless it can play host to the most spectacular of sunsets.

Rayners Lane, its neighbour, is the point at which the Piccadilly line, heading up from Sudbury, joins the Metropolitan and shares its tracks all the way to Uxbridge.

When it opened the place was called Rayners Lane Halt, and served a few scattered village cottages and little else. Harrow Garden Village slowly washed up around it, and the station was finally remade in the 1930s by Charles Holden, whose buildings I've met before, and who made sure to stamp his signature motifs - the flat roof, the geometric shapes, the glass ticket hall - here as elsewhere.

By necessity it's a sprawling place, but not especially bustling, the trains shunting to and fro at their own pace with little sense of wanting to go anywhere. Well, to go anywhere fast. The sun was sinking low when I stopped off, casting the whole place into deep, sentimental shadow.

Eastcote is also Charles Holden's handiwork, bordered, as seems so often to be the case along this line, by tiny antiquated-looking businesses and musty corner shops that nobody goes in.

Ruislip Manor is the same, albeit lacking the grandeur its name implies.

Ruislip was, for a time, the only stop between Harrow and Uxbridge and has, perhaps understandably, more of the look and feel of a proper branch line station than its predecessors:

Ickenham was the next to open in chronological terms, but you wouldn't think it surveying its dismal structure today. The building was completely demolished and rebuilt in the 1970s. It's surely one of the grottiest and most unwelcoming edifices on the whole Metropolitan line.

Except for the platforms, that is:

Hillingdon was the last stop to be added to this branch of the line and therefore the last new station to be added to the Metropolitan in its entirety.

It spent two decades loitering under the name of Hillingdon (Swakeleys), and is still referred to as such on signs on the platforms. Its present condition, though, is far removed from its antecedent, and literally so. In 1992 an entirely new version of Hillingdon station was opened, south of the original, to enable the A40 to be expanded and re-routed. As such you can now stand on the platform and, rather eerily, watch one of London's major arterial roads rumble beneath you. It's a fantastically designed place, full of gleaming corridors and giant walkways that won it the title of Underground Station of the Year 1992, but which seem utterly at odds with its location out in the middle of nowhere, hard to reach, and next to a dual carriageway.

Finally, then, to Uxbridge, where the Metropolitan came to rest on 4th July 1904, a little way to the north of where the station is today. Its present form is another Holden creation, topped off by a pair of sculptures over the entrance depicting giant mechanical wheels with leaf springs.

It's a cavernous, rather impressive place, totally at odds with its immediate surroundings - Uxbridge's noisy, ramshackle shopping precinct - and, with its stained glass and canopy roof, seems to have arrived straight from another age.

And that was it. The end of the Metropolitan line. No more tiny branches to investigate, no more dead ends to explore, no more Metro-land lingering over the horizon. It felt like an epic trek was concluding in, as usual, a profoundly underwhelming fashion. Uxbridge town centre, despite once being the setting for Press Gang - the best children's TV series ever - was no gold at the end of the rainbow. The value of this excursion had been the journey itself, not the arrival at a destination. All change, please. All change.

Metropolitan Line: Moor Park - Amersham

This stretch of the London Underground, being neither in London nor underground, exists in a world of its own.

It bears none of the symbols of the rest of the network: crowded carriages, gruff commuters, regular services, and mile upon mile of darkness. Instead it operates at a pace and in a manner entirely divorced from its parent.

Trains are infrequent. Carriages are almost empty. You can sit in a station for ages, entirely at the whim of whoever is - or isn't - at the controls. And you pass through landscape so beautiful and undisturbed as to suggest you aren't so much in a different county but a different country.

North of Moor Park the line divides yet again, with one branch curling off towards Watford. To ride this service is like taking a Sunday afternoon excursion along a miniature railway. You pass through fields and forest, with trees bending right over the line to form a dense tunnel of foliage. I saw foxes, hares and squirrels alongside the track. It really is as far removed from any notion of an Underground railway as it's possible to get. Here's a photo of the line I took from a bridge outside Croxley station:

The Metropolitan reached here in 1925. Initially the station was named after the village: Croxley Green, a charming place and thoroughly, unashamedly, rural. It reverted to its present title after the Second World War.

The Herfordshire countryside intrudes right onto the platforms:

After Croxley it's but a few miles and minutes to Watford, though the station, such as it is, is no way a direct link to the town. It sits far out on the edge of the suburbs and resembles, much like Mill Hill East, a terminus by default. Originally the line was to have continued into the town centre, and recently plans have been revived to try and achieve just that. For the time being, though, it's a curious cul-de-sac into an unlikely port in the middle of nowhere.

If you take the other branch from Moor Park you're following mainline services towards Buckinghamshire. As late as 1961, Rickmansworth station was the point at which Metropolitan line trains bound for London switched from steam to electric locomotives. Up until then, if you wanted to travel north of here you'd find yourself being decoupled from your swish diesel service to a wheezing, hissing steam engine hailing from the back end of 19th century. Electrification of the line was seen as less of a priority, clearly, in this backwater of the Underground.

Rickmansworth, like many of its neighbours, seems to pride itself on its horticultural exhibitionism, and so it should:

Chorleywood, meanwhile...

...is even more at one with nature:

By now I was passing through stations that felt untouched for over 100 years, where the arrival of a train seemed almost an inconvenience, disturbing the tranquil inertia and unapologetic calm.

Chalfont and Latimer opened in 1889 to serve the numerous similarly-named, quaintly-titled Chiltern outcrops of Chalfont St Giles, Chalfont St Peter and Little Chalfont. Entering the station was like going through the door of a village hall.

Here the line divides yet another time, offering a choice of destinations: Chesham or Amersham. Chesham is a dead end, served during the day by a desultory four-carriage train that goes back and forth, back and forth every half hour or so. It's possibly the least integrated example of public transport on the whole network. The train leaves when it feels like it and arrives likewise. I sat on it in Chalfont and Latimer for 25 minutes before it moved an inch.

Chesham itself, opened in 1889, is a real end of the line place. It has the longest distance between adjacent stops on the entire London Underground, and is the most westerly station there is.

Unmanned, somewhat ill-kept and not a place to want to linger, its only appeal - when I was there - was its view across the Chess valley towards the rest of Buckinghamshire.

Its neighbour, Amersham, is the resting place of all through-services on the Metropolitan. By dint of being on a mainline route it's nowhere near as disheartening as Chesham, but you're still at the mercies of the system as to when the next London-bound train will be leaving. When I was there, campaigners were handing out leaflets to try and stop the planned closure of the ticket office.

I might have had more sympathy for them had they not made the central point of their argument the rather fusty claim that the Oyster card was "complicated". It's nothing of the sort!

As John Betjeman took great trouble to point out, the Metropolitan didn't always end here. Originally services continued, on to Great Missenden, Wendover, Stoke Mandeville and Aylesbury (up to 1961), and also beyond, even further into Buckinghamshire, to Waddesdon Manor, Quainton Road, Granborough Road, Winslow Road, and Verney Junction (up to 1936).

The latter was conceived by captains of industry to be one of the great interchanges of the country, on a par with Crewe or Clapham, with trains from the north joining the Metropolitan to rush all the way down to London, through the city, onto the coast and, spectacularly, under the sea to France.

Such ambition seems preposterous nowadays, at a time when it takes almost 20 years to merely get agreement to build a single new railway to run from the west of the capital to the east. But at least those engineers and planners had the inclination to dream.

They also had the foresight and willpower to extend the Metropolitan deep, deep into the shires outside London, thereby allowing the city's residents and workers an ongoing chance to escape into the restorative meadows of Metro-land.

Metropolitan Line: Harrow-on-the-Hill - Moor Park

There are two ways north out of Harrow on the Metropolitan, and both - thankfully - quickly shake off the dour atmosphere of the station and its surrounding area.

One route spirals towards Uxbridge; the other strikes out for Hertfordshire and, ultimately, Buckinghamshire. I was now travelling through a part of the Underground network that had always, by virtue of its distance from the city centre, seemed to me to have an air of otherworldliness.

What were all those stations doing so far from central London, in travelcard zones that were so remote they needed not numbers but letters? Why did the line have so many branches and peculiar offshoots? What kind of tiny places were these, joined artificially to the likes of the swaggering Baker Street and Kings Cross?

Rattling towards the Hertfordshire border in a carriage of ever-diminishing passengers, the first stop is North Harrow. There's a tangible difference in the air between this station and its predecessor, effectively summed up by the way there's a door out of the booking hall directly into a coffee shop. There's also a wonderfully parochial shop next door (Soles And Heels), which is part-ironmonger, part-shoemaker, and which looks like it's been there for 60 years.

When the Metropolitan first passed this way in 1885, there was no reason for trains to stop here because - as with other stations further down the line - there was nothing to stop for. It wasn't until 1915 that passengers could get on and off, presumably to have a cup of tea or a get a key cut.

A feeling of staid, unruffled suburbia intensifies at Pinner.

The trains did stop here as early as 1885, but only to attend to folk dwelling in the tiny village and surrounding farmland. The very name Pinner seems to embody a certain, well, frame of mind or attitude to life. It's a place where cosy primetime sitcoms take place. It's a place from where people write letters to broadsheet newspapers. It's a place where people settle, rather than simply somewhere to live. This is the view from the station bridge back towards Harrow (the church spire is on the horizon):

Northwood Hills didn't open until 1933. The titular greenery can be seen in the distance, disclosing the fact that the area isn't actually on a hill at all. There were two old women waiting by this entrance, watching me with piqued curiosity and discussing - inevitably - the weather.

Northwood station, meanwhile, is another of the 1887 vintage and currently covered in scaffolding. When I was there it was also full of schoolkids on their way home, eyeing me suspiciously. This bloke, though, didn't seem to care what I was doing.

Pulling into Moor Park you're finally out of Greater London, into Hertfordshire and more or less on a regional branch line rather than an urban public transport system.

It's a lovely station, reeking of days gone by, full of brown colours and old oak panelling, and originally built purely to serve patrons of the local golf club. Indeed, its original name was Sandy Lodge. Standing on its platforms, surrounded by trees on all sides, a few buildings in the distance, peace and quiet everywhere, it's possible to believe you're hundreds of miles away from London and fully ready to hear the sound of a steam engine in the distance.

But this still isn't the end of the Metropolitan line.