The World Chess Solving Championship, which has been held annually since 1977, is the premier solving event of the year, and the centrepiece of the World Congress of Chess Composition. It is held over two days and consists of six timed rounds, each featuring three examples of a particular genre. Teams consist of three solvers, with the two highest scores for each round being combined to make the team total for that round. A fourth solver solves solely as an individual, and a country may enter two additional solvers in the juniors, seniors or women categories. Great Britain won the team title in 1986, 2005, 2006 and 2007, and shared the title with the USSR in 1990. Two British solvers have won the individual world title, Jonathan Mestel in 1997 and John Nunn in 2004, 2007 and 2010.