Above is another slam deal from the congress. After North opened one club and rebid one spade, South went through fourth suit forcing (to game) and supported spades to show slam interest. North cue bid the ace of clubs, then South asked for key cards, the response of five spades showing two key cards and the queen of trumps. Having found that all the key cards and the queen of trumps were present South now had a problem. If North had good clubs or the diamond king, then seven spades was likely to be a good contract, otherwise six spades or maybe six notrump was probably best. The suggested bid at this point is six clubs. Normally a bid of six of a suit asks for a third round control, but here it should show the club king. North, with the hand held could now jump to seven spades. With the king of diamonds and worse clubs e.g. AJxxxx North might now bid six diamonds.
Every pair bid to slam, only two pairs bid the grand, about a third of the field bid six notrump and the rest six spades.