So here are the traffic lights with a circular white on blue arrow sign on them indicating motorists must drive straight ahead and not turn right or left, (those wanting to turn left have their own unsignalled lane by the traffic lights) : -
https://maps.app.goo.gl/25RCwanvFSVDmiUJ7Each signal head has one of these signs, so a total of
three separate signs which would have been visible on approach and also illuminated at night. If you say "the only signs are on the traffic lights which are not immediately visible at night", then sorry, it is game over at London Tribunals. However, I am puzzled why the council have not put 'No Right Turn' signs on these signal heads. One could say the straight ahead arrows are misleading, and NRT signs would be much better, but it's not a strong argument.