Just spoke to Keith Gasson (Lewisham Council) and he said that one of the speed meters had average speed of 21-22mph - I expect that was on Derby Hill and other one had lower speeds. And those lower speeds will still need 3 humps as 20pmh zones require humps on certain distances.

Waste of money if you ask me. Can't understand why humps are not placed strategically where cars can build up speeds to slow them and allow natural road curve/hill/ narrowness to slow speeds at other places.

I am all for putting 20mph sign at boundaries to remind the post van that these are residential roads.