This framework of wood and wire-netting (chicken wire the Americans call it) was devised as a means to prevent enemy stick grenades from lodging on the roof of the tank.
The pair of tail wheels on a Mark I tank seem to fascinate most people; they are in fact the rump of the articulated Landship idea devised by Colonel Crompton.
It was realised soon after the start of the First World War that it was going to be a much lengthier and consequently more expensive war than first expected.
One object, The Henriques Ring, now on display in the new Tank Men exhibition offers a fascinating and very personal link to the first tank attack in history.
The Tank Museum has produced a book that is essential reading for anyone involved in family history wishing to trace ancestors in the various British tank regiments.