The stone built, slate roof little structure still in place south of the extension.
Try to imagine pre- 1990 or even much earlier, an outside toilet - with a fantastic view of the Wrekin.
Has had a few repairs 2013-2016, and some acceptance into the patio/garden, south of the extension.
Can assume that it hasn't been used for 50+ years, and has not been excavated. Should you find an archeologist who wants to look :)