The truck is an AEC matador, a heavy haulage unit that saw military service with the British Armed Forces from about 1939 to 1952. Many were spun off into civilian ownership and there are still quite a few around today (2017). This truck is marked for the Ministry of Aviation and it appear to have a generator mounted inside on the back. With its paint scheme and roof mounted warning lights its intended for use on the manoeuvring area somewhere.
Edward Angus tells atchistory that the Matador generator was originally part of the GCA setup- it replaced the original Diamond T mounted generator. The trailer is a RAF pattern 13ft sigs container simply trailer mounted.
Edward also provided this picture showing the Matador generator truck in use, possibly at Heathrow but it could have been any of the Ministry aerodromes that were GCA equipped. .