I reckon that the truck is an Austin K5 'Portee and Fire' to GS conversion. I've found a couple of photos of the same type amongst my Dad's pictures. This would also be a just-postwar shot as he didn't get hold of a camera until then.
L4697229 is listed as 3 ton 4x4 a/t portee from contract V4866. The plate above the radiator is the flash protector to allow forward firing. The conversion seems to have retained the soft-top cab and much of the portee stick set.
Rich