White Shield, by the brewery of the same name, was awarded the top prize at Camra's Bottled Beer Competition, sponsored by The Guardian newspaper. The silver medal went to Greene King's Hen's Tooth, and Staffordshire-based brewery Titanic won bronze with its Titanic Stout.
Also at the festival, which opened at Earl's Court this week, Crouch Vale Brewery's Brewer's Gold was voted best beer in Britain for the second year in a row by a panel of brewers, beer writers and journalists.
MD Colin Bocking said: "I am speechless. It was enough of a surprise to have won Champion Beer of Britain in 2005, but to have been voted Britain's best beer for a second year in a row is truly unbelievable."
The silver award went to Harveys brewery in Sussex for its Sussex Best Bitter. The Bronze was awarded to Triple fff brewery in Hampshire for Moondance.