Northern Line: Camden Town - Kennington (via Bank)

Apparently there were plans in the late 1980s to run this part of the Northern Line, together with the High Barnet branch, as a completely separate Underground service. Maps were even produced for London Transport perusal, with the "new" line coloured a disgusting bile green.

Expediency probably overruled such a plan ever becoming reality, but there's something to be said for avoiding all the congestion created by having one line with so many branches and intersections. The Bank branch takes longer to get to Kennington than the Charing Cross branch, though it's not clear on the Underground map. Things appear to get off to a good start with trains bypassing Mornington Crescent and heading straight for...

Euston. It's then less than a minute to get to King's Cross St Pancras.

That's less than one minute to get to the King's Cross St Pancras Underground platforms. Not the station ticket hall. Nor the two titular mainline stations. Embroiled in seemingly never-ending renovation, to get from St Pancras Underground station to St Pancras mainline station you currently have to walk ages to get into the open air, whereupon you find yourself next to King's Cross mainline station, meaning you then have to walk ages to get to St Pancras and so on. This visitor-unfriendly arrangement is, however, going to be at least partly curtailed in November this year when the pompous sounding St Pancras International opens for business.

Anyhow, what you can see of the Underground station looks very nice indeed, as you'd expect for a completely redone interchange. It's topped in terms of excellence, though, by Angel.

It's undoubtedly one of my favourite stations to date, chiefly by virtue of being so cool. The air conditioning is incredible. On the (as usual) boiling hot day I was travelling this stretch of the Northern line, I was more than happy to loiter a few minutes on Angel's platforms. Or rather, The Angel. It's never been called this officially, but colloquially the extra article has been around for decades, cemented in the popular consciousness by that edition of Forty Minutes from the late 80s, The Heart Of The Angel.

Back then the station, built in 1901, was one of the worst in the land: grotty, falling apart and plagued by lifts that never worked and a rather blinkered, flippant staff (at least, this was how they were depicted on camera). Shortly afterwards, however, it was shut, completely rebuilt and now represents surely one of the best stations on the network: clean, fresh and with the longest escalators in Western Europe.

Old Street, also built in 1901, is a complete contrast: it lives under a roundabout, with no buildings on surface level at all.

There's another abandoned station just before Old Street: City Road, closed in 1922 and all building work, including the platforms, subsequently removed.

Bits of Moorgate date back to 1865, but the whole place was done over in the 1960s to better incorporate that other bit of the Northern Line which doesn't exist anymore, but at the same time does: the bit from Moorgate to Finsbury Park. Now run by First Capital Connect, I don't know why this line isn't more used or better promoted. Maybe the answer's in the question: namely, it's run by First Capital Connect. There are about seven different entrances to Moorgate from the street. This isn't strictly one of them, but it's the nicest.

Bank station, or The Bank as train drivers stubbornly call it, is lacking a proper surface entrance like Old Street. But then it is right next to the Bank of England and Royal Exchange buildings. And it's part of that sprawling, complicated jumble of tunnels that joins it and Monument station into one uber-interchange the length of an entire street. And one of the exits is *inside* the Bank of England itself. To be honest, it's quicker to walk from one to the other above ground.

London Bridge is a bad interchange if you're trying to hop from the Northern to the Jubilee Line. There's no hopping involved, more like a long schlepp. Albeit in part along one of those magical moving walkways. The Jubilee platforms are way nicer than the stuffy, skanky Northern ones, but then since they were only built a decade or so ago that's no surprise. London Bridge itself is the oldest station in the city, dating back to 1838. It's got a really imperial entrance.

Borough, on the other hand, has a tiny front door and no escalators.

Apparently things used to be far worse, with - until recently - precious little having been done by way of renovation since 1890. It looks great outside, though, with that concrete roundel on the roof.

And so to Elephant & Castle, a right roustabout of a station with, if you choose to leave by one of the two entrances, no particularly striking buildingwork at all. Typically, this was the one I went for. The other entrance is your familiar Leslie Green-styled affair, of the kind I've already encountered at Kentish Town and Mornington Crescent. No photos of that, I'm afraid. Just this glum atrium.

The end was in sight. Here's Kennington again, this time with that classic dome in shot.

Northern Line: Camden Town - Kennington (via Charing Cross)

After coming together in rather disjointed union at Camden Town, almost immediately the Northern Line splits again, one route heading south through the West End, the other heading south via the City. The former, seemingly forever referred to as the Charing Cross Branch, appears to get you south of the river faster than the other one, but as with anything to do with the Northern Line, appearances have nothing to do with reality. The City branch, for instance, gets you to Euston quicker than the Charing Cross branch, thanks to the latter making its first stop at...

Opened in 1907, it's always been one of the lesser-used Underground stations, so much so that when it closed for six years in the 1990s nobody really noticed. Fittingly its re-opening was attended by the surviving practioners of the eponymous I'm Sorry I Haven't A Clue game. There's a plaque to Willie Rushton somewhere or other. I've never seen anyone get off at Mornington Crescent. Fact.

After Euston, gateway to the north...

...with its ludicrously overheated Underground tunnels and statue of the London-Birmingham Railway founder Robert Stephenson, it's but a particularly aeronautical stone's throw to...

Warren Street. Many's the time I've got off a train early or walked on to Euston rather than plunge into the humid depths of this dank, dark station. Its platforms are badly-lit and like an oven, even in winter. It's another 1907 vintage, ditto Goodge Street:

As is suggested by the fact it looks like it's squatting in an otherwise unexceptional block of flats, the station has no room for escalators, only four worryingly tatty lifts. It's another station that has a World War 2 deep-level air-raid shelter underneath it - the one, in fact, from which Eisenhower broadcast the announcement of the invasion of France on 6th June 1944.

To be honest, if you're travelling along any part of this branch of the Northern Line, it's quicker to walk. From Warren Street to Embankment you get stations every five-10 minutes on foot. Tottenham Court Road is even less of a stone's throw from Goodge Street.

Another manky station, befitting the clatter and grime that gets whipped up on Oxford Street, I don't think I've ever used this station and not felt myself physically getting dirtier and sweatier the further down I go. The infrastructure dates back to 1900. The smells do too. Perhaps if the long-mooted Crossrail service ever gets built, the whole station will get totally rebuilt.

Leicester Square is far better, though I'm probably speaking more out of familiarity with the station I used for a year or so to get to work.

Leslie Green was the architect of the original 1906 building; Charles Holden gave it a spring clean. There used to be a busker in this station who played the harp. The story of Charing Cross is a melee of name-changes, station-mergers and pretend-connections. The present day station is actually two combined: Trafalgar Square, originally on the Bakerloo Line, and Charing Cross, solely on the Northern Line. There was soon another station to the north, Charing Cross (Strand), which quickly lost its first two names, and Charing Cross (Embankment), which lost its last name. Then when the Jubilee Line was extended through to the area in the 1970s, everything was rolled up into one. Except Embankment, as it was now called, which still exists - less than 60 seconds walking distance from its parent, ten times as far if you use the Underground, and quicker to reach than the end of this paragraph. Under the river it's Waterloo... ...and then on to Kennington: Newly refurbished, it still bears traces of its construction in 1890 as part of London's first deep-level line, the City & South London Railway. It's also a pleasantly leafy and lazy rendezvous where the Northern Line becomes one again.