Let's answer that question via an unusual method - a collection of tube maps.
You'll have seen Central London Tube Maps on the tube, the DLR, the Overground and the Elizabeth line. They show a large chunk of the transport network to help you plan jour journey once you leave the line you're travelling on. But they're all different, this because the spaces they have to fill aboard the trains are very different sizes.
Comparing them would once have been very time-consuming and involved travelling on all kinds of trains. But those maps have now been bundled up as part of an FoI request so we can all see the full set.
The map above is the version displayed on the Jubilee and Northern lines - the same on each. That's unusual, indeed no other lines share identical maps. Most lines in fact need two different maps, this because the spaces for maps in the carriages have different proportions. Within the FoI files I counted 18 different maps across the TfL estate, which is an awful lot of different kinds of Central London.
This is a very broad Central London, as seen on the Victoria line.
It stretches west as far as Heathrow and east almost to Upminster, but from north to south only manages to include the Victoria line from King's Cross to Vauxhall.
And this is a rather squarer Central London, also seen on the Victoria line.
It stretches north and south far enough to show the entire line, but west no further than Shepherd's Bush and east only as far as the Isle of Dogs.
If you're on the Circle line, Waterloo & City line or DLR you'll be able to see the whole of your journey on the Central London Tube Map. If you're on the Central, District, Jubilee, Northern, Piccadilly or Elizabeth lines it might well fall off the edge.
I've looked to see where the southern edge is on all 18 maps. On half of them the Northern line stops at Kennington, still in zone 1, but on the other nine maps it goes further. The final station is Oval on the Central line map, Clapham North on the Piccadilly and Victoria maps , Clapham Common on the Bakerloo and DLR maps, and Tooting Bec on the other DLR map. Only on the Overground and Elizabeth line maps does the Northern line appear all the way down to Morden.
Heading east on the District line: As far as Bow Road on two of the maps, East Ham on two, Barking on three, Upney on one, Elm Park on four, Hornchurch on five and all the way to Upminster on just one. Heading north on the Piccadilly line: As far as King's Cross on seven of the maps, Finsbury Park on two, Manor House on two, Turnpike Lane on one, Wood Green on two, Bounds Green on one, Arnos Grove on one and all the way to Cockfosters on just two. Heading west on the Central line: As far as Shepherd's Bush on four of the maps, White City on one, East Acton on five, North Acton on two, Perivale on two and Greenford on four. None of the 18 maps get anywhere near West Ruislip.
It's all remarkably varied and intrinsically inconsistent, this because the maps are subtly different sizes and because each line demands a different focus.
But I can summarise the lot in a potentially useful way by seeing which stations appear on all 18 maps. Identify the overlap and you have the definitive Central London Tube Map.
» The whole of zone 1 appears, as you'd expect.
» The only line to appear in its entirety is the Waterloo & City.
» The Circle line nearly appears in full, but four stations beyond Latimer Road are missing.
» Geographically, the northernmost station on the map is Hackney Downs, the easternmost is Island Gardens, the southernmost is East Putney and the westernmost is Latimer Road.
» Two stations in zone 3 appear - East Putney and Cutty Sark (both in the zone 2/3 overlap)
Urban centres that don't appear include Brixton, Hammersmith, Camden and Stratford. Stratford is perhaps the most surprising omission, but that's because it's missing on the Bakerloo and Victoria lines which go nowhere near and whose maps are squarish.
It's not a perfect representation of central London because it goes too far out in some directions and not quite far enough in others, but it is arguably the most important part of London's rail network because it appears on all 18 Central London Tube Maps.
