British tank stowage item identification

[Jakko Westerbeke]

I don’t recall seeing it in photos of Normandy or beyond, or even Italy except Sicily, so it looks to me like a desert-only item, yes. But it’s unlikely to be a tent or shelter or similar, because first of all it’s very small even if the thick back folds open/out, and second, a good number of of tanks in the desert carried a rolled-up tarp along one side of the hull to use as a shelter — including some of those that also have this unknown item on them.

I suspect that I’ll just have to make something that looks like what I see in the photos (as the reason I’m asking about this thing is to put it on a 1:35 scale model).