After six months of wondering why I have this strange uncomfortable feeling, my chair always slides to the right when I'm at the desk, and the "carpet protector" the chair stands on keeps migrating south, I checked.
The floor in my study slopes 4.2° down to the south.
Pesky Elizabethan builders ... hadn't they heard of spirit levels?
I once lived in a rented cottage, which was four hundred and thirty five years old. It was actually one half of a bigger house that had been divided by a centre wall, and all the floors and sundries sloped towards the other half/house, to the extent that if you just dropped, flopped, or collapsed into the settee, it would roll backwards "downhill" until it came up against the dresser, three or four feet behind. When the novelty faded, I put some chocks under the wheels.
Even Drunk one never lost one's sea legs Mr Slasher,the problem arose when one was taken drunk shoreside and one's legs still insisted on compensating for yaw and pitch that weren't there resulting in departure from controlled walking.
What ho Mr Keef. A few years back, number one brother who's a builder was commisioned to build a plywood plinth to cure a problem of a similar nature. The trick is to build it back far enough so you dont fall off it and to feather the edges so you don't keep tripping over them!
I was thinking along the same lines as WM... To still have the convenience of being able to move your chair forward and backwards and sideways, find 6ft x 6ft of floorboards (the ones that slot together), then level that with a 5" x 5" on the south side