Well it seems walking tube lines is becoming ever more popular. The video above shows James Borrell and his girlfriend Jess walking the Victoria Line from Brixton to Walthamstow Central. Really brought back a lot of memories for me.
The Victoria line is one of the few lines I've actually walked both ways. For my Tube Challenge I walked it in the opposite direction, but I have also walked from Brixton to Walthamstow Central in a rare London blizzard.
If you do want to walk a tube line, it's a great one to start with as it's the second shortest after the Waterloo & City line.
You can read my account of walking in the opposite direction here: Victoria Line Walk – From Walthamstow Central to Brixton