追記:奥の変なのは架橋戦車の「チャーチル・グレートイースタン」(Churchill Great Eastern)です。
実戦には参加してないようです。

EDIT: That weird thing in the background is an "AVLB,":https://en.wikipedia.org/wiki/Armoured_vehicle-launched_bridge "”Churchill Great Eastern”.":https://en.wikipedia.org/wiki/Cecil_Vandepeer_Clarke#The_Great_Eastern
Apparently it was never used in action.