The bidding was West 1C, North 1S and West 1NT.

1NT contracts often involve a lot of detective work, and this one is no exception.

Declarer and Dummy have 22 points. North has 5 spades, almost certainly including the K, and probably 10-14 points. With more points North might have bid on, or overcalled 1NT originally.

1. North might lead a spade, won by the SQ. The CK wins trick 2 and the CA takes the CJ at trick 3. (Playing North for a doubleton CA is an unlikely play, but in this case would have been a winning one.) North leads another spade. Declarer has 6 certain tricks, and there would be a lot of sense in taking the SA and continuing with a spade to let North take his 3 spade tricks. It often helps to let opponents open up a new suit, but one needs to be careful that you have reasonable discards available. Declarer discards a diamond and a heart, and Dummy discards a club and a heart. What does South discard? Let us assume 2 hearts and a diamond, since anything else would be fatal for the defence. Now, North must lead a heart, because a diamond would allow South to eventually be thrown in with a club. With that excellent defence, Declarer will be restricted to 6 tricks.

2. North may feel that a spade lead will not be good, and he might decide to lead the D2.

2.1 South will probably play the DQ, and Declarer should win, to avoid a spade switch from South. Declarer now knows that North has 4 diamonds including the DJ. He almost certainly has the DK as well, because a lead from Jxxx would not be attractive compared with a spade.

Declarer leads to the CK, which wins. So North also has at least Ax in clubs. This is 11 'known' points and 11 'known' cards. Since this maybe Declarer's only entry to Dummy, and South almost certainly has at least one of the missing heart honours, it would seem sensible to take a heart finesse before knocking out North's CA. The choice is between the HQ and the H3, but it would be best to lead the HQ, because this might pin a singleton HJ in North's hand. South covers with the HK and Declarer wins the HA. Declarer now continues with the H10.

(a) If South wins the HJ and leads a spade, Declarer must win the SA, and throw North in with the CA. The Defence will be limited to 1 heart, 1 club, 3 diamonds and the SK. Declarer makes 1 diamond, 2 clubs, 2 hearts and 2 spades.

(b) If South lets the H10 win, then he will not gain the lead and Declarer will make the same 7 tricks more easily.

2.2 South may get lucky and play the D9 at trick 1. Because North would not have led low from KQJ2, Declarer knows South must have an honour, and therefore an entry. However, Declarer must still win the DA, and continue as above. However, Declarer is likely to be held to 6 tricks, because South will have the extra entry with the DQ.