 Complete the following phrase:  Keene has also been involved in organising several World Championship finals matches. He arranged for the first half of the World Chess Championship 1986 return match between Kasparov and Karpov in London. The match, however, made a loss for the British Chess Federation BCF and, for reasons never clarified, he resigned from his position in the BCF shortly afterwards. He organised the 1993 PCA World Championship match between Kasparov and Nigel Short in London, for which he was one of the official commentators along with Grandmasters Jonathan Speelman and Daniel King. He was the instrumental force behind Brain Games, which organized the 