Each of these 125 problems has won top prize in one of the many chess competitions held throughout the world- and they will help hone players' skills so that even beginners can learn to become winners too. As with all orthodox chess conundrums, the ones collected here stipulate that White makes the first move, and must checkmate Black in a specified number of moves no matter what Black does. This specification is inviolable: players can neither make more moves nor fewer, and each problem has only one correct key. A section offers hints for the really, truly stumped. But beware: while most hints provide instant help, some cryptic ones require a little extra thinking. About Mensa:- Mensa is the internationally renowned high IQ society which has a worldwide membership of almost 100,000 members in more than 100 countries. There are 28,000 members in the UK, including 2,200 Junior Mensans under the age of 16. To join Mensa, the only requirement for membership is that an individual's IQ falls within the top 2 per cent of the population.