We've seen this location before. The signs have two displays, one for 40 mph during the day, and one for "Flying Motorbike" during the restricted night hours, this is to prevent "cruising" and other car-related unsocial behaviour.
As far as I recall, one appeal at London Tribunals won on the basis that the sign did not convey the full TRO, in tht there is no information on the sign as to when the restriction applies, so it is impossible to find this out.
There may be an avance warning sign, but the last time I looked in GSV, it wasm't sufficiently up-to-date, so you may have to do some legwork with a camera.