(Based On Ruling at EBL Workshop 2018)
Contract 5♦ by South
Dummy wins West’s ♥K lead, but declarer revokes with ♣6. A diamond trump from dummy is won by West’s ace. The defence then cash their two club winners, and then West, for want of something better to do, plays ♥Q, which declarer ruffs (another revoke). Declarer then claims the remainder of the tricks, but whilst showing his hand, East notices a heart amongst declarer’s long diamonds.