I have seen mention of a MkI experimentally fited up as a minesweeper. Apparently this consisted of suspending some form of electro magnet in front of the tank (presumably to lift mines out of the soil). One gathers that it didn't work. This predates the Mk V** fitted with mine exploding rollers. Does anyone have any further details?
That is indeed the mine lifter. In "The Britsh Mark I Tank 1916", David Fletcher says that it didn't work and that it was probably supposed to be operated by a soldier working the crane hoist from the ground. If it had worked, you would hope that the controls for the crane were moved inside!
Finally obtained a copy of "A New Excalibur" and on page 203, there is a shot of a Mk IV fitted with mine detonating rollers. Another for your "funnies" collection Treadhead .