On what turned out to be a good day for Anand yet again, the Indian ace used the hidden dynamics out of a decent opening to beat Hammer, who was outdone under pressure.
Grandmaster Anish Giri of Holland threw the tournament open for Anand as he beat Topalov in a long drawn game.
In the other decisive game of the day, World champion Magnus Carlsen found his winning touch against Levon Aronian of Armenia. Maxime Vachier-Lagrave of France held Hikaru Nakamura to a draw, while Alxander Grischuk signed peace with Fabiano Caruana of Italy.
Topalov needs a draw with white but his style of chess is uncompromising, which might give Anand a chance to have a go against his 2010 world championship rival.
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It may be recalled that Anand had beaten Topalov with black in the famous 12th and final game of the 2010 world championship.
Nakamura and Giri share the third spot on five points each, while Carlsen improved his statistics to jump to joint fifth along with Caruana and Vachier-Lagrave on 3.5 points each. Aronian and Grischuk are joint eighth on three points, a full point ahead of last-placed Hammer in this 10-player round-robin tournament that is a part of the Grand Chess tour.
Carlsen referred to an interesting conversation with Hammer, who said he didn't understand why everyone was playing the English opening with him. As he confessed, Carlsen told him: "Everyone will play the English with you", to which Hammer said "not Anand, he never plays bad openings".
As it happened, it was the English by Anand that floored the Norwegian for the fourth time in the tournament.