Source: ACBL Bulletins
Bidding commentary: After South overcalls 4, North is surely worth a Roman Key Card Blackwood effort. Partner’s response of 5 shows two key cards plus the Q. Given the bidding, it looks like all you are missing is the
Lead commentary: When a preemptive bidder doubles a slam contract with partner on lead, he tells partner, “Don’t lead my suit, don’t lead a trump. I almost certainly have a void. Lead it!”
Defensive commentary: West can look at his hand and figure out that partner’s void must be in diamonds, so he should lead one! On the diamond lead, East ruffs and cashes the A for down one, plus 200. Any other lead results in minus 1660. This double of a voluntarily bid slam is called a Lightner Slam Double after its originator, Teddy Lightner. The conventional double asks for an unusual lead (not the doubler’s suit and not a trump, both common leads against slams).
Further commentary: Against a notrump contract, the double asks partner to lead dummy’s first-bid suit. When the double is made against a suit contract – especially by a player who has bid preemptively – it almost always means the doubler is void in a suit and is hoping the opening leader can work out which one.