The real ale was hailed as the GBBF swung open its doors, with more that 55,000 people expected to attend the five-day event and more than 800 different tipples on offer.
The festival, staged by CAMRA, the Campaign for Real Ale, raises a glass to beer brewed using traditional ingredients and left to mature in the cask from which it is served rather than industrial-scale, pasteurised lager carbonated with carbon dioxide.
"It was a really tough decision but Elland 1872 Porter is a fantastic beer and a well deserved winner," said CAMRA chairman Colin Valentine.
"A 6.5 percent, rich and strongly flavoured porter with flavours of coffee and dark chocolate, this result makes it two years in a row that our champion winter beer has gone on to win the champion beer of Britain competition."
Elland's head brewer Michael Wynnyczuk said he was "utterly shocked".
"After we won the winter ales competition you wonder about it in the summer GBBF competition, as people may prefer different styles of beer in warmer weather," he said.
"But it's a great beer and we're really proud to be crowned champion beer of Britain."
Second place went to Twitchell by Hertfordshire brewery Buntingford, which won the bitter category. Jarl, made by Argyll brewers Fyne Ales, the golden ales category winner, came third.
CAMRA says its membership has grown from 65,000 to 150,000 in the last decade, with women now accounting for 22 percent.
While overall beer sales have dropped in Britain by more than 500 million pints in the last three years, real ale sales have held up well and even enjoyed a small increase in 2011.
"There are now more than 1,000 breweries brewing in excess of 8,000 different real ales for consumers to choose from," Valentine said.
"More people are looking for something brewed locally and with so many breweries in Britain, everybody has a local beer to try."
"It's very exciting that more and more women are trying real ale."
"Now it is increasingly seen as a drink for women as well as men. That trend will help put the whole British beer market back on a track towards growth."