What's the longest tube journey where the station names keep getting longer?
Let's have a look at some maps.
For example...
Edgware (7 letters)
Burnt Oak (8 letters)
Colindale (9 letters)
Hendon Central (13 letters)
...but it all goes wrong at the next station, Brent Cross, because that's only 10 letters.
So that's a chain of four stations.
The top of the Jubilee line is even shorter because Canons Park and Queensbury both have 10 letters so that halts any increasing chain.
You might expect the longest chain to start at Bank, a four-letter tube station in zone 1 that's on several different tube lines. So let's have a look.
The Central line west gets no further than Chancery Lane (because Holborn is much shorter).
The Central line east halts at Liverpool Street (a dead end in all directions).
The Northern line stutters only as far as Old Street or London Bridge.
If you're willing to accept that Bank and Monument are separate stations then we can get a chain of 5.
Bank (4) → Monument (8) → Tower Hill (9) → Aldgate East (11) → Liverpool Street (15)
The trick is to hop on the Waterloo & City line to Waterloo and continue from there. There are several 4s.
Bank (4) → Waterloo (8) → Southwark (9) → London Bridge (12)
Bank (4) → Waterloo (8) → Kennington (10) → Elephant & Castle (15)
Bank (4) → Waterloo (8) → Lambeth North (12) → Elephant & Castle (15)
Bank (4) → Waterloo (8) → Westminster (11) → St James's Park (12)
But if we head north on the Northern line we can hit 6.
What we have here, topologically, is a network of one-way arcs.
There's no predictability to the arrows, it's almost like tossing a coin for each to see which way it points.
Also some of the links can't be traversed (for example Oxford Circus, Warren Street and Goodge Street all have 12 letters so you can't pass between them).
Looking at the arrowed map I think I've found the longest route and I believe it starts here.
There is a 5 here by going south...
Pimlico (7) → Vauxhall (8) → Stockwell (9) → Clapham North (12) → Clapham Common (13)
...but it's best to go north.
Take the Victoria line from Pimlico(7) to Victoria(8) and on to Green Park(9).
Then change to the Jubilee line through Bond Street (10) to Baker Street (11).
St John's Wood is also 11 so we can't go there. But if we switch to the Metropolitan line we can bypass it to Finchley Road (12), then switch back to the Jubilee for one more stop to West Hampstead (13).
What's particularly brilliant about this longest route is that it increases by one letter each time.
Pimlico(7) → Victoria(8) → Green Park(9) → Bond Street(10) → Baker Street(11) → Finchley Road(12) → West Hampstead(13)
It's easily done in less than 30 minutes, not that I recommend you give it a go.
If you allow the challenge to extend to any stations on the tube map, you can add one more to the chain by switching to the Overground.
Pimlico(7) → Victoria(8) → Green Park(9) → Bond Street(10) → Baker Street(11) → Finchley Road(12) → West Hampstead(13) → Finchley Road & Frognal(20)
That's eight stations in a row, each with a longer name than the station before, which I believe is the maximum possible.
It ought to be possible to check this with some cunning coding, because fundamentally this is a directional network problem. But to the best of my old-school knowledge, the longest chain of lengthening tube stations is 7 and the longest chain on the tube map is 8.
