Just wanted to mention that in all my 40 something years of being born and bred in Yorkshire, I have NEVER heard the expression "tenfoot" though it might be an East Yorks thing.
It's basically a back alley that runs behind a row of terraced houses for anyone that cba to google. These are very common but I've never known them called tenfoots. For example you'd have Websleuths Street and behind it would be called Back Websleuths Street aka back road or back alley. These would typically be a narrow road with access to small yards at the backs of the houses, probably containing bins (and a thrown out sofa / mattress / fridge or two!)
The one they're searching looks slightly different to what I have described, as instead of another row of houses on the other side of the tenfoot there is grass with sheds on and then the river