The tournament is being held at the Institution of Engineering and Technology, Savoy Place - just off The Strand in London. The picture shows the statue of Michael Faraday that stands outside.
Because of regular scandals involving players apparently receiving outside help from a computer, spectators had to leave our phones and tables in the cloakroom, pass through an airport-style metal detector and submit to being passed over front and back by wand-style detectors too.
With players tiring and the tension rising, today's round (the 12th) turned out to be the most dramatic so far.
Before the tournament started, Norway's Magnus Carlsen was a firm favourite, with Lev Aronian seen today as as his only realistic challenger. Today both of them lost. Aronian is out of contention and Carlsen has lost the lead of Vladimir Kramnik of Russia.
Kramnik was a protege of Garry Kasparov and took his world title in 2000, holding it until 2007 (though like the world heavyweight boxing title the picture has got complicated in recent years). In many ways he is the last great representative of the Soviet school of chess that dominated the game for most of the 20th century.
Perhaps I am getting old, but I cannot help feeling that the young and motivated Kasparov would have had little trouble winning this tournament. Certainly, Magnus Carlsen's approach of nursing small advantages for hours until his opponent crumbles, effective though it is, lacks the crowd appeal of Kasparov, Fischer, Spassky and Tal.
The English grandmaster Nigel Short, who lost a world tile match to Kasparov himself in 1993, was holding court in the commentary room and was hugely impressive. Every now and then he said something that made it clear how infinitely greater his grasp of the game is than that of a former club and county player like me. Other past English greats in attendance included Bill Harston and Jon Speelman.
And who did I spy in the corner of the refreshment room but Evan Harris and Simon Hughes?