Lest it be thought that there are double standards for officers, as has been alleged, I can relate a story told to me by an old chum who was an ensign in the Welsh Guards at the time of the incident. Going home for the weekend, he bumped into his adjutant at Paddington. Spotting the fact that my chum had committed the heinous offence of wearing brown shoes in London (in civvies), the adjutant ordered him back to Wellington Barracks, where he spent the weekend on regimental duties as a punishment.
Not quite 3 weeks detention, but then wearing brown shoes wasn't quite in the same category as making an arse of yourself in the public gaze.