China's Li Haotong walks down the 18th fairway during the final round of the 146th Open Championship at Royal Birkdale in Southport, Britain, July 22, 2017. [Photo/Agencies]

He survived a major wobble in the last round at Birkdale to finish 12-under and beat compatriot Matt Kuchar by three shots.

Spieth was already the fourth-youngest man to capture two majors with his 2015 double, having previously become the youngest winner on the PGA Tour in over 80 years at the John Deere Classic in 2013.

Adding to his achievements, Spieth warmed up for Birkdale with a victory at the Travelers Championship last month which allowed him to match Tiger Woods in reaching double digits for tour wins by such a young age.

Along with Nicklaus, the other players to have completed the career Grand Slam are Woods, Ben Hogan, Gary Player and Gene Sarazen.

But Spieth is not a fan of comparisons between him and the all-time greats of the sport.

"To be in that company, no doubt is absolutely incredible. And I certainly appreciate it ... but that kind of comparison is still a long way off. Still, we work really hard to have that, with that being the goal," said Spieth after becoming the youngest British Open champion since 22-year-old Seve Ballesteros won at Royal Lytham in 1979.

His victory, and the manner of it, drew praise from Nicklaus.

"He's won 11 tournaments and I had won eight before 24," Nicklaus, now 77, wrote on Twitter on Sunday.

"If you look at his victory total, his win today and the way he won, Jordan has shown an amazing display of maturity for someone so young, and he has been doing that for a quite a while.

"I think it's wonderful."

AP - AFP