Opening 4NT asks partner to name any ace he might hold. In response, 5C says ‘I have no aces’; 5D shows the ace of diamonds; 5H the ace of hearts; 5S the ace of spades; and 6C the ace of clubs. With two aces responder bids 5NT. (One partnership actually has a mechanism to uncover which two aces are held, but such refinement puts a lot of strain on the memory for little likely reward.)
John Murdoch sat West at the Falkirk Teams Championship, and gave the convention its once-in-a-decade outing. This hand is perfect: if partner shows no aces he signs off in 5H; if partner shows an ace he signs off in 6H; and if partner shows two aces he bids 7NT. A bad diamond break might sink his contract, but that would be extremely unlucky. On this occasion breaks were normal and John was soon claiming 12 tricks and 980.
He did not expect to gain 14 imps for such a simple auction. His counterpart in the other team (a player not yet able to use the Senior Moment as an excuse) had an aberration – as Victor Goldberg used to say, a Cow Flew By. He persuaded himself that the 6C response showed two aces and bid 7H. A lucky player gets a club lead and finesses to discard his spade, but not this time: North knew what 6C meant, and his spade lead sank the contract.