New: All Vubridge

As South you reach a pushy grand slam in spades and West thinks he's found a safe lead with the ♥K.

A count of tricks shows there to be seven spades (assuming no 4-0 trump split), one heart, three dimaonds and a club - a total of twelve "on top". The thirteenth trick may materialize from either the diamonds breaking 3-3 or from the club finesse.

The first point of technique is for South to ruff the opening lead in hand - if he were to take the ♥A he wouldn't know what to discard on it; either a diamond or the ♣Q discard would reduce declarer's options. So  declarer ruffs the heart lead, draws trumps and carefully throws a club from dummy on the third trump. Why? Because there is a third chance to make the grand slam that we haven't yet mentioned - the hearts might be 4-4. If they are then the heart length on table must be preserved.

Now it's a case of testing all the chances (leaving the club finesse until last). Diamond to dummy, heart ruff, diamond to dummy heart ruff. Now the third round of diamonds exposes the diamond break. If both opponents follow the hand is over - declarer throws the ♣Q on the ♥A and claims. As it is, the diamonds are 4-2 so declarer tries Plan B. He cashes the ♥A, throwing the now useless diamond.

If the hearts break 4-4 (and they are on this layout) then declarer can throw the ♣Q on the last heart and claim. If hearts were 5-3 then (as a last resort) declarer would fall back on the club finesse.

Was that a "safe" ♥K lead? No! A trump lead (or a diamond lead) would have beaten 7♠ as declarer would have lacked the entries to take three heart ruffs in hand and reached the established heart.