Development of the World Chess Championship became the first unified and undisputed World Chess Champion since Kasparov split from FIDE to form the PCA in 1993. Kramnik played to defend his title at the World Chess Championship 2007 in Mexico. This was an 8-player double round robin tournament, the same format as was used for the FIDE World Chess Championship 2005. This tournament was won by Viswanathan Anand. Because Anand's World Chess Champion title was won in a tournament rather than a match, a minority of commentators questioned the validity of his title. Kramnik also made ambiguous comments about the value of Anand's title, but did
World Senior Chess Championship the men's section. So far one male World Chess Champion – Vasily Smyslov – has gone on to win the World Senior Championship as well (at age of 70 in 1991). He has also been the first Senior World Chess Champion ever. Nona Gaprindashvili is the only female World Chess Champion to obtain the World Senior title as well. The oldest World Senior Champion, male or female - before the split in two different age categories has been made - is Viktor Korchnoi who won the title at age of 75 and a half (in 2006, his only participation). Vlastimil