" The best man. You know? He hands you the ring and has to marry the bride if you ran away and so on. The Dean's been reading up on it, haven't you, Dean?"
"Oh, yes," said the Dean, who'd spent all the previous day with "Lady Deirdre Waggon's Book of Etiquette". "She's got to marry someone once she's turned up. You can't have unmarried brides flapping around the place, being a danger to society."
"I completely forgot about a best man!" said Vimes. "

― Terry Pratchett , Men at Arms (Discworld, #15; City Watch #2)