It's a guess, but the lorry underneath appears to be an AEC Mammoth Major MkIII. Dinky just call it 'Horse-Box'
The Horse Box was added to the range in 1953 as number 581. It was maroon with maroon wheels and in British Railways livery. If anyone can tell me why a nationalised railway network needed a horse box would they please let me know. Also was it the horse box that was for hire or the horses?
As the poor old Americans would not have understood what a British Railway was they got a special export version without the British Railways decals. The model had a number change in 1954 to 980 and then remained in production until 1960.
All of these are scarce and sought after and attract high prices, the US Export versions especially so. According to Ramsay though the version made for one year (581; 1953/4) is worth a lot less than the one made for six years (981; 1954/60) which I find odd.