Window or door?

This site of several derelict single-storey shops has been earmarked for residential development.

Hopefully that will be done in character with rest of the facades on Upper Bristol Road, Bath.

However, if it is, this interesting end gable shot will surely disappear.

It doesn't seem tall enough to be a door; perhaps it was a window blocked up centuries ago when the government introduced a tax on windows?

As there are no other such features, I'm assuming it wasn't uncovered by the destruction of an adjacent building during the Bath Blitz, when WW2 bombing hit parts of Bath.

I'm sure there are a surfeit of historians in Bath who can explain this mystery...