Too young for this blog but one could argue this is a prewar technology throughout. It's a 1946 Model 18, using the cradle frame of the prewar ES2 and still the Norton girder forks. Remarkably, the front brake sits on the right hand side of the machine on these models. Other differences are a cleaned-up gearbox cover and a smaller headlamp. Compare this ES2 to the 1946 16H that featured earlier on these pages.
The registration plate would have been issued by Middlesex C.C. (currently llford London NE).