British tank stowage item identification
 

Does anyone know what this item is that is seen hanging off a good number of British tanks in North Africa and Sicily?

Attachment 140957Attachment 140956

I’ve also seen it on some Crusaders, and it never seems to be rolled up more than in these two photos. I can’t work out what it is, or is for, let alone how it’s actually constructed. It seems to have two thin panels on one side and a larger, padded part on the side that’s always towards the tank?