Rumbelow

Chief Postal Inspector Rumbelow was a big man with a face like toothache and was the scourge of the Ankh-Morpork Post Office when Tolliver Groat was a young man. He was worse than the gods to the hapless postmen under him, as at least gods forgive...

He went down in postal folklore for being the man to stop the dread Mail Sorting Engine. This had become dangerously unstable thanks to Bergholt Stuttley Johnson's idiot notion of using pi as exactly 3, rather than three point mumble mumble and a bit and thus distorting the universe. The wizards warned that stopping it would end the universe, but CPI Rumbelow eventually ordered everyone else out and belted it until it stopped. When asked why he had risked destroying the universe, he answered thus; "Well, I figured that if I did no-one would notice, plus when I hit it the first time the wizards legged it, so unless they had another universe to go to it meant they weren't certain..."