From VP Gores invention... the interweb...
The strength of beers has climbed during the later years of the 20th century. Vetter 33, a 10.5% abv (33 degrees Plato, hence Vetter "33"), doppelbock, was listed in the 1994 Guinness Book of World Records as the strongest beer at that time, though Samichlaus, by the Swiss brewer Hürlimann, had also been listed by the Guinness Book of World Records as the strongest at 14% abv.
Since then, some brewers have used champagne yeasts to increase the alcohol content of their beers. Samuel Adams reached 20% abv with Millennium, and then surpassed that amount to 25.6% abv with Utopias. The strongest beer brewed in Britain was Baz's Super Brew by Parish Brewery, a 23% abv beer. The beer that is claimed to be the strongest yet made is Sink The Bismarck!, a 41% abv IPA, made by BrewDog, who also made Tactical Nuclear Penguin, a 32% abv Imperial Stout, using the eisbock method of freeze distilling - in November 2009 the brewery freeze distilled a 10% ale, gradually removing the ice until the beer reached 32% abv. The German brewery Schorschbräu's Schorschbock—a 31% abv eisbock, and Hair of the Dog's Dave—a 29% abv barley wine made in 1994, both used the same freeze distilling method.