The Belladonna coup is the play of a low card away from an accompanying high card, giving the opponents the impossible choice between setting up a winner for declarer and abandoning an attack on another suit.
The provenance of the following spectacular hand, which illustrates the Belladonna coup, is uncertain. A similar layout, with the same key play, is discussed by Victor Mollo. Both sources attribute the coup to Giorgio Belladonna, for many years a cornerstone of the Italian Blue Team. (Belladonna later said that he could not recall having made the key play.) It is said that Belladonna played it as described in a European Community championship in Belgium during the 1980s. But it is also said that Paul Lukacs, the game's pre-eminent composer of single-dummy problems, composed it away from the table.
Against South's 4♠, West leads a small trump to East's ♠10 and South's ♠J. South has several ways to play for ten tricks, which include finding the ♥A onside (50% probability of success), or finding the diamonds 3-3 (36%). The best prospect is to ruff a heart in dummy, but the attack on trumps jeopardizes that plan. If South mis-times the play, the defense can manage to lead three rounds of trumps and win the ♠K, before declarer can ruff the third heart.
Instead of relying on the position of the heart ace or a favorable diamond split, South played for the nearly sure thing by taking a safety play in hearts.
South led to dummy's ♦K and played the ♥6 away from the ♥K! This gave the E-W an impossible choice:
Notice that South gives up the best chance of making a heart trick (leading toward the ♥K). By giving up the chance for one trick in hearts, South virtually guarantees ten tricks (now only a very unlikely defensive minor suit ruff can defeat the contract).
Notice the presence of the avoidance play theme in this deal.