World Champion Viswanathan Anand let go off an excellent position to lose to Hikaru Nakamura of United States in the fourth round of the London Chess Classic on Wednesday.
After 11 successive draws in a row, including nine draws in the just concluded Tal Memorial at Moscow, the loss on Wednesday proved to be too costly for Anand as he fell to joint seventh spot in the nine-player round robin tournament, wherein the soccer-like scoring system is in use.
World number one Magnus Carlsen played out a draw with Vladimir Kramnik of Russia and was joined by Luke McShane of England at the top the table with eight points after four rounds.
McShane, an amateur by choice, continued his excellent run and won against compatriot David Howell.
In another game of the day, former world championship challenger Nigel Short opened his account at the expense of country-mate Michael Adams.
With Carlsen and McShane in front, Nakamura now occupies the sole third position with seven points, while Kramnik is in fourth with five points in his kitty.
Not far behind is Levon Aronian with four points so far while Short jumped to the sixth spot with three points.
Anand, Howell and Adams share the seventh spot with just two points apiece.
There are five more rounds still to go, and Kramnik, Aronian, Anand and Short have played one game less than the others, and this may prove crucial in the rounds to come.
It was a King's Indian defense by Nakamura and Anand went for the Bayonet attack and chose a variation that Nakamura had faced a year back against Kramnik.
It was clear that Anand was much better prepared as Nakamura lost an important tempi to let the World Champion enjoy a substantial advantage.
Anand, however, missed the thread of the position in a dominating position and one mistake proved crucial as Nakamura came back in the game with some imaginative display. The game lasted 49 moves.
Speaking about the result Nakamura said: "Of course beating the world champion for the first time is very special."
Carlsen tried but could not make headways against Kramnik. The queen pawn opening by the Norwegian fizzled out in to an opposite coloured Bishops endgame in quick time and thereafter it was just a draw.
McShane won his second game in a row, thanks to an optical blunder by Howell. It was about equal position out of a Scotch opening when Howell went for a wrong queen sacrifice leading to disaster.
Short finally struck form with a hard-earned victory. Adams was surprised in a side variation of the French defense and even as he had slightly better prospects out of the opening, Short fought his way back and cruised to an important victory.
Meanwhile, in the open section, former world junior and current national champion Abhijeet Gupta won his fourth game on the trot to share the lead with compatriot International Master Sahaj Grover and British duo of Gawain Jones and Jovanka Houska.
Results: Rd 4: V Anand (Ind, 2) lost to Hikaru Nakamura (USA, 7); Magnus Carlsen (Nor, 8) drew with Vladimir Kramnik (Rus, 5); David Howell (Eng, 2) lost to Luke McShane (Eng, 8); Michael Adams (Eng, 2) lost to Nigel Short (Eng, 3).