After a particularly orgiastic 6th year disco, when half the prefects were caught sack-deep in pupils from another school's 6th year, the assembled culprits were given a mass bollocking by the headmaster.

The climax of his harangue was the instruction "...and if the urge ever comes over you again, get a box, stand on it and shag one Mr. Bain's cows". (Mr. Bain ran the nearby farm.)

After that, every time someone got the horn, they would murmur "I could just stand on a box..."