I think the person in the picture is a police officer in one of the Ministry of Defence Police units prior to their amalgamation.
http://www.paintedships.com/modpolice.asp
They officers were issued with caps to wear when travelling to and from work so they did not have to wear helmets or flat caps.
If you contact the Ministry of Defence Police museum at Wethersfield, Essex I am sure the curator will be able to look up the collar (warrant) number for you.
Not convinced at the mo...
I was in a previous existance, the Practice Nurse for the MDPGA based at Whetherfield, and was privy to the museum there, and the collection of hats in the main building. I have never seen such a uniform there, and as they were "special constables" in thier early life, I would expect to see some form of black and white band or some such on the uniform.
There is a greater chance of course that this chap is one of the various cadet organisations that wore uniform at that time such as the CLB!
