Where (and what) is this ?

OK, just come across this thread by mistake, and FIVE years too late!

If anyone is sill watching it my immediate thought was Pillbox (but then for anyone who knows me that will be no surprise )

The openings have stepped sides just as the majority of pillboxes do. One side has two openings, a common RAF thing. Grass covered roof, well again many pillboxes did have grass on their roofs.

The one area of problem for me is the double layer, two story pillboxes do exist, but all of those that I have seen are two floors of exactly the same size.

I still say pillbox, mainly in the vain hope of finding a new pattern

John