On arriving at Duxford for the Military Vehicles day and MAFVA Nationals in June 2009, this lovely combination was to be found parked up on the grass behind the arena, near the Land Warfare Hall.  I managed to get this series of photos before it was surrounded by other visitors and hopefully there is lots of useful detail here for anyone wanting to try their hand at one of these.  For modeiing combinations there is the 1/76 example of the Diamond T and the Rogers now done by Revell (the ex-Matchbox kit).  If you like 1/35, then both the tractor and trailer are available as resin models from Wespe Models.  They also do a Caterpillar variant, as do Resicast, which might make for such an impressive combination as this one.