Sponsons were built separately from tanks, not necessarily by the company that built the actual tanks.
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.
David Fletcher talks through the Mark I tank, in this Tank Chat, the world’s only surviving example of the tank.
Historian Dan Snow presents this bite size history of the tank in the First World War, filmed on location at The Tank Museum.
The Tank Museum’s tank is the only surviving example of a Mark I Tank.