The London Chess Classic has been exciting, and round 4 was the bloodthirstiest round of all. Three of the four games were decisive, and it wasn't too far from being a clean sweep.
Magnus Carlsen entered the round in clear first, and almost went out that way. Coming out of the opening, one might have thought that Vladimir Kramnik had achieved equality or at least an easily drawn ending. Carlsen's preparation or over the board assessment was more accurate, and it was incredibly impressive to see him outplay Kramnik in an opposite-colored bishop ending. Fortunately for Kramnik, Carlsen played 25.gxh6 rather than 25.Rxh6, and while Black still had to suffer a while the draw was within reach, and Kramnik managed to save the game.
Luke McShane thus caught Carlsen in first by defeated David Howell. McShane could have been in clear first by a fair margin had he defeated Carlsen earlier in the tournament, but then again he was worse today until Howell uncorked consecutive errors on moves 28 and 29.
In the other battle of Britain Nigel Short defeated Michael Adams, who clearly isn't in good form here. Short hadn't been in good form either, but he played quite well today, outplaying Adams on the black side of a Tarrasch French with 3...h6.
Finally, Hikaru Nakamura was the third player to win with Black, defeating Viswanathan Anand in a King's Indian. Nakamura once again played the dangerous 9...Ne8 line he has used (with some success) against other world-class players, but this round's version with the unfortunate 13...h6 + 18...h5 two-step certainly favored White. As Nakamura noted, however, Anand is a relative newcomer to 1.d4, and his feel for the King's Indian isn't yet what it is for Nakamura, simply as a matter of experience. White was better, but in a very complicated position his 29.Nc4? not only lost the advantage but may have left him with a lost position - and in the end, a loss.
So after four rounds and going into the one plenary rest day, Carlsen and McShane lead with 8 points apiece (on the 3-1-0 scoring system in use there), Nakamura has 7 and Kramnik (a game behind) has 5. Aronian has 4 and Short has 3, and they too have already had their byes. Anand, like Adams and Howell, has just two points, but unlike them he has already had his bye.
Update: Games here, with notes to Anand-Nakamura.