I was there (you can see me on my Dad's shoulders in a couple of the pictures). I think someone said there were about 120 people in all.
It was great! The rain held off and there was the unexpected treat of a (professional?) singer singing some old waterman associated songs from the late 18th/early 19th century (apologies if I have got the history wrong).

I didn't stay for the lecture - my Dad's span of attention is not that good, but the walk was really good for making you look at all the familiar places with a little insight into what went before.

Thanks to Steve Grindlay, the singer and everyone else involved in making it happen.