A computer glitch caused by a bra forced Marks & Spencer to shut 31 shops yesterday. The boob was caused by a special offer programmed into the chain's computer system on Wednesday night. Customers were offered £3 off any two brassieres, but M&S bestsellers such as the modern minimiser bra, padded bandeau bra, and halterneck secret support vest refused to register with bar code scanners. This sent till systems into spasm, forcing shop closures in towns such as Dumfries, Kent and Portsmouth. According to M&S, which claims one third of all British bra sales, the special offer was one of 27,000 price changes fed into its computer system that night. "It became clear that tills in the affected stores were working very, very slowly, so the only choice was to restart the whole system," a representative told today's Times. "Some stores were shut for about 30 minutes and others for an hour and a half. Only two (Hounslow and Portsmouth) were closed all day." Disgruntled shopper Amanda-Jane Doran from Tunbridge Wells said: "I'd just dropped the kids off at school, and I was heading for M&S for chicken, birthday cards, wrapping paper and booze which you can't get in one shop anywhere else." "But we were turned away at the door by a very nice lady who said all the computers had broken down." ® Related stories UK high street clueless about Web Chicks in their underwear online now Armageddon off with blood sports bra Is it a bra, or an anti-mugging device?