I've being trying, vainly, to find some illustration that shows the layout of Tritton's second trench tractor design. I have found some descriptive detail (size of wheels, length width, T shaped front, two driver positions, two machine guns etc etc.) I've used this to try an construct an impression. http://img.villagephotos.com/p/2005-11/1114252/tritton2.jpg The machine was powered by electric motors and the electricity was to be supplied by a traction engine mounted generator behind the front line. As the trench tractor advanced it would pay out cable which would be buried by a plougn shear haulled behind the beast. The machine was not a tank as we understand it - more a short range APC to get troops across no mans land and into the enemy's front line trenches. If it had advanced further and crossed uncleared enemy trenches its power cable would have been exposed to cutting (by grenade perhaps) effectively stranding the monster. I'm aware that I've had to rely on a lot of guess work so if any one as more and/or better info please supply it. (and whilst I'm on the subject dare I say 15 ton Tim?)
David Fletcher has drawings at Bovington - both later scale drawings by Dick Harley (part of his and David's classic series in 'Tankette') and also drawings used by Tritton himself (I think) to illustrate a lecture he gave in the early 1920s (IIRC). Unfortunately, I completely failed to copy any when I was down there a few months ago, but if you contact David F I'm sure he'll help.