They call it the "big mo," as in momentum, and it just swung heavily in favor of challenger Veselin Topalov, after an uncharacteristic blunder from World champion Viswanathan Anand sensationally put their 12-game match back in the balance at 4-4.
In a totally drawn opposite color bishop ending, Anand, who easily found the correct drawing maneuver with 50 ...h4!, unexpectedly gifted his challenger a full point with his faulty follow-up of 54...Bc6??, when all he had to do was protect the h7 pawn with his bishop to secure the draw.
His immediate resignation followed, as he didn't wish to sit through the agony of the winning sequence (as pointed out live on Chess.FM and on GOTD by commentator GM Joel Benjamin) of: 56 g4 Bd7 57 g5 Be8 58 Bg7 Bd7 59 g6 hxg6 60 Kxg6 and Black is helpless to prevent White from penetrating and winning.
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And after so carefully nurturing his advantage in the match, Anand's costly mistake now goes down in the annals as one of the biggest howlers in a world championship match - and one that could well pass the momentum to Topalov going down the home straight with just four games left to play.
So why not sign-up for ICC today (click here to join) to get the all best in chess commentary as the World Championship looks set to go to the wire? And each match day on Chess.FM, we will also have GOTD and New In Chess trivia, where members can win ICC extensions and and a 1-year subscription to the world's best chess magazine, New In Chess.