Double trouble

In honor of my newly improved posting system* -- now with bidding diagrams! -- here is a case in which bidding plays a critical role.

North	East	South	West
1	Pass	1	Pass
3	Pass	4	Dbl
Pass	Pass	Pass

Lead:  K

North

 A 10 4

 10 6 4

 A K Q 10

 7 4 2

West

 J 8 7 3 2

 A 7 2

 7 3

 K J 10 8

East

 --

 J 9 8 5 3

 8 5 4

 A 6 5 3

South

 K Q 9 6 5

 K Q

 J 9 6 2

 Q 9

After trumping the third round of clubs, South's usual play would be to lead three high trumps, which in this case would go down. West would be left to win a trump trick plus a heart and two clubs. Playing the spade king first to test the suit would also lose a trump trick.

But West's double led South to guess, correctly, at the dangerous trump split. So South led the 9, which was covered with the jack and the ace, and the details of how the contract was made are left to the reader. If West had held her tongue, the contract would have neatly gone down.

Doubling a contract when holding a void or singleton in trump, which I've been doing for years but which we may call a Matos double after certain notable recent instances, is therefore doubly clever. East is privy to the same information as West in this deal, and a double from that side would yield no useful clues.

*Tell me if the diagram looks funny on your browser. The posting tool should work in the comments too, so hop right in if you have something to say!