South of Baker Street is where you leap forward several decades, and where the line becomes far more functional. Between here and London Bridge it's interchanges all the way, apart from Southwark, a station invented purely to serve Waterloo East mainline station and which isn't in Southwark at all.
You get a different kind of passenger on this stretch of the line: no-nonsense, hurried and often weighed down by numerous tourist-esque accoutrements. There's no quicker way of getting from the north west of London to the south east, but it's usually a grim, crowded and hassled experience.
The tunnels south of Baker Street were built in the mid-1970s as part of an extension to what was to have been called the Fleet Line. The plan was to have dug all the way to Charing Cross and then on along Fleet Street to stations at Aldwych, Ludgate Circus, Cannon Street, Fenchurch Street, St Katharine Docks, Wapping and then under the River Thames to New Cross, terminating at Lewisham.
Inevitably the money ran out. The extension was only built up to Charing Cross, which is where the now-renamed Jubilee Line terminated upon opening officially on 1st May 1979.
An alternative plan was then drawn up to extend it parallel with the River Thames, on from Wapping to Thamesmead via Surrey Docks North, Canary Wharf, North Greenwich, Custom House, Silvertown, Woolwich Arsenal and ultimately to Thamesmead. This too, however, was binned and for ages it looked like the Jubilee would run up to Charing Cross and no further.
Of course, the new Charing Cross interchange was itself something of a mess, constituting bits of the old Trafalgar Square and Strand stations (on the Bakerloo and Northern lines respectively), a reconfiguration that had also involved renaming the existing Charing Cross station on the District and Circle lines as Embankment.
All that convoluted and costly revamping, however, got junked completely in the 1990s when the extension finally got underway - not along Fleet Street, but, at the behest of big business in Docklands, south via Waterloo and London Bridge then east to Canary Wharf. More on that later.
What happens today is that the Jubilee Line (renamed from Fleet in 1977) travels to Bond Street and Green Park as before, then swerves away from its original course to hit Westminster. In fact if you watch from the carriage window you can clearly see the point at which the old, now-disused tunnel peels off to Charing Cross.
Bond Street is a grim place above ground, lurking underneath an unremarkable shopping centre at one of the busiest points on Oxford Street.
Virtually no elements of the original 1900 Central Line station survive. Its Jubilee Line platforms, though, have a brusque, tidy air about them; not qualities you can apply to Green Park, which seems to have been designed to induce people to want to exit its premises as soon as possible:
Both of these Jubilee interchanges were opened on 1st May 1979, as was the original terminus, which then closed on November 19th 1999.
I remember well scores of newspaper headlines bemoaning the cost of and delay in the Jubilee Line extension. There was a particular palaver surrounding the new Westminster interchange, no doubt inspired by it being in parliament's back yard and the fact it was the last of the new stations to open to the public (22nd December 1999).
But it was worth the wait, for Westminster station turned out to be an absolutely awe-inspiring creation. It is without doubt one of the best stations on the entire network. Every time I enter it my breath is taken away. The scale, the design, the sheer ambition: it's incredible.
Its construction was a feat of marvel itself. Each of the new stations on the extension was meant to be an architectural wonder, and was contracted out to different designers. Those responsible for Westminster, Michael Hopkins & Partners, began by digging a giant 39-metre hole underneath the existing station to house all the escalators, lifts and platforms - the deepest-ever excavation in central London.
Then they faced the difficulty of constructing the station around the Circle and District line tracks, which had to be kept in operation throughout. To fit in with the design, these tracks had to be lowered by 300 millimetres - something achieved a handful of millimetres at a time during the few hours each night that the Underground was closed.
At the same time, the towering Portcullis House directly above the station was being built. For a few years that patch of ground by Westminster Bridge and opposite the Palace of Westminster was a shocking eyesore - but, again, it was all worth it.
The station's design won a 2001 Royal Institute of British Architects award, and anyone with unblinkered eyes will realise why. Massive concrete beams and columns criss-cross the interior, rising up and below stainless steel walkways, staircases and elevators. It feels like you're walking on the set of a futuristic TV show, but one made in the 1960s; in other words, an idealisation of the 21st century from a 20th century viewpoint. Utter genius.
From here on things can only be something of an anti-climax. The interchange at Waterloo, which opened on 24th September 24 1999, is notable only for its rather neat moving walkway helping to shorten the massive distance between the Jubilee and Bakerloo/Northern line platforms. Otherwise the gleaming silver-panelling and metallic walkways are kind of overshadowed by the sprawling, confusing layout. There's no trace of any of this, ironically, above ground:
You get a complete change from classical to modern when you reach Southwark, which opened on 20th November 1999, and which is currently the newest station on the whole network.
As mentioned above, it suffers from not really having a point to its existence, but makes up for it by virtue of its compact yet striking layout. Designed by Richard MacCormac of MacCormac Jamieson Prichard, it's a maze-like structure weaving in and out of the Victorian railway viaduct carrying trains from Waterloo East and Charing Cross railway station across the Thames.
As such Southwark station boasts not one but two concourses at different levels. The first has the inspired touch of a glass roof allowing natural light to penetrate right down into its heart. There's also a superfluous yet stunning glass wall 40 metres long, consisting of 660 specially cut pieces of blue glass, designed by the artist Alexander Beleschenko.
Then you have to go down escalators to reach the platform-level concourse, itself on two levels, with features like unpolished steel panels and metal beacons - apparently, according to MacCormac, inspired by the designs of the 19th century Prussian architect Karl Friedrich Schinkel.
Suffice to say during rush hour there's barely time to notice let alone appreciate any of this.
Finally, on this leg, to London Bridge, the Jubilee Line part of which opened 7th October 1999.
Once again, major reconstruction work was needed to incorporate the new line and, once again, much congestion of the surrounding streets was the result. The volume of passengers now using the Jubilee as a means of leaving this part of London, however, makes you wonder what conditions were like before the line passed this way.
Oh, and apparently during excavations to create the new booking hall, numerous Roman remains were found. Some of these are supposed to be on display somewhere in the station. I've never seen them. Perhaps that's because I'm always too distracted by all those food stalls offering fresh salads and pastries. The commuters' menace, I tells you!