If one opponent plays a critical card in a suit, his partner is twice as likely to have the adjacent card in the same suit. This is because of the Principle of Restricted Choice (“PRC”) – a mathematical theory that was found to have relevance at the bridge table by Terence Reese. He first expounded the theory in his epic book “The Expert Game”, written in 1958 – an inspirational read for any ambitious player.

Dealer South N/S Vul
 A 10 5 3 2 A Q 3 A Q 3 K Q Q 9 8 10 9 8 6 8 4 2 9 7 5 J 5 4 2 10 9 6 5 10 8 4 3 2 K 7 6 4 K J 7 K J 7 A J 6
 West North East South 1 Pass 4NT Pass 5 Pass 5NT Pass 6 Pass 7 Pass Pass Pass
North used the Blackwood convention (4NT) to ask for aces, and when his partner’s 5 response (one ace) revealed that all aces were present, he bid 5NT to ask for kings. South’s 6response indicated possession of the three missing kings so North bid the Grand Slam. West’s 10 lead ran to declarer’s J and declarer cashed K. East’s J fell and declarer used PRC to deduce that West was now twice as likely to hold the adjacent card – Q. Thus when he followed by leading 4 and West played 9, he crossed his fingers and inserted 10. East discarded a so he breathed a sigh of relief, cashed A felling West’s Q, and claimed his Grand Slam. ANDREW’S TIP: When one opponent plays a critical card in a suit, play his partner to have the adjacent card in the same suit.