Came across this Tube routing puzzle in
http://londonist.com/2013/02/can-you...m_medium=email
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Have you ever heard that there is one possible route around the Underground
taking in every single line for just one stop? One of our friends was told
this puzzle and, being a London geek — hooray — he worked it out over
several commutes. Can you? Remember, you must visit each different line for
just one stop.

Clues:

The route includes the Overground and DLR
You can change from one line to another, even if they continue on the same
tracks (e.g. Go one stop on the Circle line then change to the District for
one stop in the same direction)
There are 4 permutations of start and end points, because only one of the
two stations for the first and last move is important (e.g. if you are on
the Victoria line and need to get to Stockwell, you can start at Brixton or
Vauxhall – it makes no difference to the rest of the route)
We think it’s high time we planned another whimsical London walk so this
route could be it. It’s not an epic one – like the Olympic walk – but it’s
an interesting one, zigzaggy, and an original way to celebrate the 150th
anniversary of the Tube, Londonist style. We’ll bring you the solution next
week.