American Eddie Kantar, a multiple world champion, still wakes up now and then, due to this deal.

E/All		♠	Q J 8
		♥	A J 9 6 5
		♦	K 8 2
		♣	A Q
♠	7 6 5 2			♠	4 3
♥	K 4 3 2			♥	Q 10 8 7
♦	J 5 3			♦	Q 10 6 4
♣	K 10			♣	7 5 4
		♠	A K 10 9
		♥	-
		♦	A 9 7
		♣	J 9 8 6 3 2

¹ Precision Club: 11-15 HCP, at least five clubs
² relay (asks for a closer description)
³ four spades
⁴ natural: five card suit, game forcing
⁵ slam try, establishing clubs as trumps

After this start something went wrong in the bidding of the Italians, very uncharacteristically, since they ended up in 7♣!

The year is 1975. The Italian Blue Team is unbeaten in world championships since almost twenty years. At last a specially formed American team is in a position to beat the Azzuri, since this deal hits the table shortly before the end of the match, the score being about equal.
Kantar, West, hears the Italians bid on to 7♣, is behind the 2♣ opener and is holding the ♣K.
'I am a world champion!' he thought, he later described.

All players at the table felt this was the decisive deal. Kantar led a heart (his partner East had doubled a 4♥ bid by North en route) and felt like the earth sank from under his feet when the ♣AQ appeared in the dummy.
Belladonna could do no better than trump the lead and play a club. On West's ♣10 he played dummy's ♣Q.
When that held the trick 'some colour reappeared on Belladonna's cheeks', as kibitzers reported. He continued with the ♣A and when the ♣K came tumbling down, the reactions at the table differed considerably. Belladonna mumbled 'sorry' to his opponents, Garozzo cast his eyes up, probably saying a prayer of thanks to the Holy St Gennaro, while Kantar threw his cards on the table, exclaiming: 'Oh, my God!!'

Italy won the title once more, thanks to this deal.
The real nightmare for Kantar had yet to start. Soon afterwards it was suggested he should have played the ♣K in the first round of clubs, thus suggesting he held that card bare. This would mean East held four clubs with the ♣10.
If the declarer would have believed in that club distribution, he could still have made his contract, provided some lucky breaks in the further distribution.
When asked, Belladonna said he indeed would have played east for four clubs if West had played the ♣K at once.
Belladonna then would have had to play for a distribution like:

E/All		♠	Q J 8
		♥	A J 9 6 5
		♦	K 8 2
		♣	A Q
♠	7 6 5			♠	4 3 2
♥	K 7 4 3 2			♥	Q 10 8
♦	J 5 4 3			♦	Q 10 6
♣	K			♣	10 7 5 4
		♠	A K 10 9
		♥	-
		♦	A 9 7
		♣	J 9 8 6 3 2

In order to make 7♣, the declarer would have to execute a trump coup. This means he would have to shorten his trump suit until it was of equal length as East's (or even shorter, as we shall see). The declarer then would work towards an end play where dummy has the lead and South holds a tenace in trumps behind East.
Here we go: after winning the club trick (West the ♣K!) with the ♣A, the declarer cashes three rounds of spades (necessary, so East will have to have three spades), ending in dummy, then the ♥A, on which South discards a diamond. The declarer then ruffs a heart in hand (the shortening of his trump suit) and cashes the ♦AK. He ruffs another heart, after which the position is:

E/All		♠	-
		♥	J
		♦	8
		♣	Q
♠	7			♠	-
♥	-			♥	-
♦	J 5			♦	-
♣	-			♣	10 7 5
		♠	10
		♥	-
		♦	-
		♣	J 9

South on lead. He ruffs the ♠10 with dummy's ♣Q, East having to underruff. Then dummy plays the ♥J or the ♦8 (doesn't matter) and East is powerless. South overruffs cheaply and has the rest.
Note that it is essential that the declarer plays three rounds of spades, since he has to cross to dummy eventually by ruffing his fourth spade.

Looking at the actual distribution, we see this line of play quickly would have led to one down, since East will ruff the third spade.
No wonder the deal has haunted Kantar for years ...and still does.