Wartime Tank Transport in England

[Richard Coutts-Smith]

Asking the truck ID question because it looks post war to me, which would date the photo.
I think the height in relation to the tank would preclude it being a shunter of any description (apart from the steering wheel...), and would point to it being on a flatbed wagon on an adjacent set of tracks, which would mean it is a military vehicle in it's own right, if you follow my train of thought( sorry, it just came out).
Thorneycroft or AEC was my first guess, as it appears to be quite a large vehicle but could not match that windscreen bottom. Such a distinctive telltale, yet I have to admit to failure.
Fortunately I may not be on my own...
Rich