KQT3 North can make a grand slam in clubs. Say east leads a safe heart.
North wins the heart lead, cashes the top diamonds, and ruffs a diamond high.
North crosses with the jack of clubs, and ruffs another diamond. North then cashes the two hearts hearts, pitching spades from his hand Finally, north crosses with the club ace and draws east's trumps. If east leads a club instead, then north uses the heart entry to get back after the first diamond ruff. 7H does not succeed - the defense takes three top hearts immediately then attacks clubs. That kills the west hand, forcing him to ruff, and never gets his spade tricks.