What's happened?

Today has been a sad one as I had to go to a funeral which I never like, no doubt like everyone else, as it does bring home ones own mortality. But that aside it did give me the opportunity for a blip of what I consider to be a superb old doorway.
Being a surveyor I notice these things and yet one other that I pointed it out to could not see anything unusual in it. Perhaps that's because A is arty and I am not! However hard I tried to work out how the door/frame got into this position I could not find a satisfactory answer....
It does not show too well in the photo but the opening itself is reasonably square but the frame and the door are not. Whilst the stonework externally may have been straightened without thought for the frame, how did the door also come to be out of square and opposite to the frame.........? I don't know.
But it's an interesting conundrum........