Ted, I think it was just down to the RAF clerk who typed up the orders, so I guess it was a Hillman Tilley . Incidentally I have noted that the SDF had an impressed Albion so I wonder if that is the one I'm trying to identify. The engine compartment looks similar to those on the Albion Refueller & Ambulance which had a hood shape that was horizontal from the side rather than sloping down towards he front. Albions like this also had fairly simple and small mudguards at the front, compared say to a Fordson Sussex, which seem to be the case with this 'horsebox'.