One of the toughest decision for a defender is whether or not to make a Lightner double against a slam. On the one hand it might be the only way to defeat the contract, but against that you might persuade your opponents to run to 6NT.
Take a look at the deal from the final set:
Realising that South was threatening to ruff something East moved to 6NT. He won the diamond lead perforce in dummy, came to hand with a heart and advanced the eight of clubs. When South played low without a care in the world declarer took his time before running it. His reward was + 1440.
North led the jack of spades and West won with the ace and played two rounds of clubs. North won with the king, but declarer had the rest, +1430 and a flat board.
Will South live to regret his double?