Stenson, who led by just one stroke at the beginning of the day, had been leading the field heading into the final round of a major for the first time.

But any thought that he may collapse under the pressure were proved wrong on one of the highest-quality final day battles in memory.

The 40-year-old birdied four of his last four holds to shoot an eight-under-par 63.

An 18-foot birdie putt on the par-three 14th was one highlight, along with with a 50-foot birdie putt from off the green on the 15th.

"This will take a while to sink in, I am still getting my bearings," the winner told the BBC afterwards.

"It seems like it was not going to be anyone else but the two of us, I am delighted to come out on top. 

"Thank you very much for a great fight.

"I want to thank my wife, my family, my team, all the hard work has helped to make this possible and my caddie Gareth Lord.

"I lost a dear friend on Wednesday morning in the States from cancer and I feel like he has been with me all week, Mike this one is for you."

His final day heroics put him on 20-under for the tournament, three clear of Mickelson, the American who managed a more-than-respectable 65 today.

The 45-year-old would have become the second oldest Open champion in history.

Another American in J. B. Holmes finished in a distant third overall, at six under, with a final-round 69.

Northern Ireland's Rory McIlroy, with 67 today, finished tied fifth with England's Tyrrell Hatton, who ended with a 68.

Defending champion Zach Johnson shot 71 to end one under, while England's Masters champion Danny Willett ended seven over.