...was what I thought seeing the NCN 57 sign outside Blackwells in Oxford (aren't I good? I went past Blackwells and didn't buy anything).

It goes to Chesham - to be precise, Chesham Underground station. Along the way there are some smashing traffic-free sections (such as the 'Phoenix Trail' railway track from Thame to Princes Risborough), some very tempting pubs, and as usual, some infeasibly steep hills. The one out of Great Missenden is one of only two on the NCN where I've had to get off and push - the other being the awesome climb out of Aberllefenni on Lon Las Cymru.

Along the way, there were two bent-round direction signs to right, and only one or two other places where the signage wasn't clear (mostly in Oxford, to be honest), which is quite good by usual NCN standards.

Obviously, having got to Chesham, I had to get back somehow: and (hoorah) it's Saturday, which means Rail Replacement Bus fun. So I cycled back (not on the NCN this time) to Haddenham, caught a train to Bicester, and then managed another five miles or so before dying and phoning Anna for a lift home.

Total 62 miles of tracks, which I might even map once the API wakes up.

Incidentally, Thame is rubbish for a lunch break. The fabulous butcher selling fabulous-looking steak, ale and Stilton pies won't heat them up; and the seemingly innocent Coronation chicken sandwich from the little bakery is now wreaking peculiar forms of vengeance on my digestive system.