Jordan Spieth's bid for another wire-to-wire Masters win fell apart in spectacular fashion on Sunday, as the 22-year-old Texan made an abysmal start to Augusta's back nine.
Having led by five strokes, Spieth followed up back-to-back dropped shots at 10 and 11 with a stunning quadruple-bogey seven at the 12th, where he found the water twice.
England's Danny Willett capitalised to claim his first major title. We take a closer look at where it all went wrong for the 2015 champion.
Two-shot swing as Spieth bogeys 10
Spieth marched to the 10th tee with a five-stroke cushion over Willett, having rolled in a curling 21-footer at the previous hole for his fourth successive birdie.
His hot streak came to an end when he found the greenside bunker with his approach shot at the hole named 'Camellia' and failed to get up and down.
However, the bogey seemed likely to be little more than a blip for the reigning champion, even though a two-putt birdie for Willett at the par-five 13th had reduced Spieth's lead to three.
Spieth slips again, with Willett closing in
The pressure on Spieth was starting to rise by the time he tapped in for a five at the 11th, moments after Willett had birdied 14 to reach four under.
Despite leading from round one, Spieth had been plagued by a tendency to hit the ball right throughout the tournament and a wild drive on 11 ensured he could not reach the green of the par four in two.
After punching out from the trees, the American appeared to be back on track when he played a gorgeous shot to eight feet.
Spieth's par putt stayed up on the high side, though, and Willett was suddenly within one following a delightful approach to the 14th.
A less than magnificent seven puts Willett in command
It is fair to say nobody could have predicted what happened next.
Spieth's tee-shot to the 155-yard 12th was shocking enough, the ball hitting the bank guarding the front of the green and tumbling back into Rae's Creek.
What followed was extraordinary. After taking a penalty drop and choosing to play from 68 yards, Spieth committed the cardinal sin of chunking his third shot into the water - the ball barely reaching the hazard, so heavy was the contact.
The two-time major winner turned away in disgust before his ball had landed, as BBC commentator Andrew Cotter reacted with amazement.
"Oh my word, he's chunked it," said Cotter. "He has chunked it and Jordan Spieth is sinking without trace at the Masters. This is extraordinary, from a player who has been so composed, so in control. Two in the water. Now what is going through his mind?"
Spieth's misery continued as he over-shot the green with his fifth, after another drop, and found a back bunker. From there, he was able to get up and down, but a seven left him three adrift of Willett - the man he had led by five.
Willett takes full advantage
Having been unexpectedly thrust into the spotlight, Willett responded superbly - holding off playing partner Lee Westwood, Dustin Johnson and a rallying Spieth, who birdied 13 and 15, to secure the green jacket.
Willett could only par the long 15th and Lee Westwood chipped in for eagle at the same hole to cut his countryman's advantage to one.
However, as Westwood and Johnson dropped shots late on - the latter double-bogeying 17 after getting within two - the new leader held his nerve.
A fine up-and-down at 17 was followed by a regulation par down the last, where Willett showed the steel of a major champion by hitting his second shot to 14 feet.
Spieth battled on in vain, but his slim hopes of completing a remarkable fightback ended with a bogey at 17.