This is not an illusion. On a recent short break in Canterbury I came across this door which is
the main entrance to a book shop. The whole building lists (leans) by about 30degrees. Because it is listed, doors had to be cut to fit. Windows had to be made to fit once the building itself was stabilized.
My inquiries revealed that the building was built around 1600 and in the 1800s the central fireplace was removed as part of a ‘refurbishment’ . It became apparent that the central fireplace acted as foundation stone so once removed not a lot was keeping the building up so the drift began.
It was not until the 1960s that the problem was identified and solved by some serious engineered steel retaining straps and underpinning. I have had to fit doors to openings that are not square due to historic movement but this is extreme to say the least.