Hi and thank you all for your comments

Sorry, there are no further clues on the back of the photo.
But to cut the file down so it was small enough, it is cropped, and actually the lady is sitting in the garden of a house and the structure you can see is part of a large window.
We know my husband's grandad Ernest was married twice (1913 & 1930), and this lady is *not* one of his wives - and the photo was in Ernest's photo collection which we have discovered following the passing of his son (i.e. my husband's Dad). Ernest had a collection which seems to range from about 1900 to about 1940 (we can guess that approximate range because we have worked-out/know who a lot of the people/places in the photos are). But this photo is a mystery...