Walking without crossing a road

[kake]

How far can you walk from Trafalgar Square without crossing a road?

A couple of years ago, as a test of the walkability of London, I set out from Trafalgar Square — the official centre of the town — one Sunday morning to see how far I could get without crossing a road or going over the same place twice. It was almost 17 miles before I ended up going round in a circle.

The author also says: I know of no other capital city where it is possible to do this. That sounds like a challenge to me! flaneurs, do you think this would work in your city?