Interesting building line.. but what is it?

[Ben WW]

While clearing our project house garden we came across this old building line at the rear of the garden.

I can only assume a small building was here due to the window aperture still visible.

The strange thing is the shape of the building, it is clearly curved meaning a likely rounded roof.. air raid shelter maybe?

The house was built in the 20's.

Thoughts..

 

[endecotp]

Nissen hut.

 

[Ben WW]

Nissen hut.

Thanks endecotp - shame I can't save it some how. There is a lot of movement in it.