Phil Mickelson became the oldest man to win

Spectators swamped the American as he marched up to the 18th green on his way to clinching a sixth major title, eight years after his last.

"It was quite unnerving, but exceptionally awesome. I don't think I've ever experienced anything like that before," said Mickelson, who won on six under par at the Ocean Course after a closing one-over-par 73.

He finished two clear of fellow American Brooks Koepka, who closed with a 74, and South Africa's Louis Oosthuizen, who signed for a 73.

Mickelson takes the record of oldest major winner from Julius Boros, who won this title in 1968 at the age of 48, and also joins England's Nick Faldo and American Lee Trevino as a six-time major winner. Only 11 players have won more.

"This is just an incredible feeling. I just believed that it was possible yet everything was saying it wasn't and I hope that others find that inspiration," added Mickelson.

"It may take a little extra work and harder effort to maintain the physicality, or maintain the skills, but gosh is it worth it in the end.

"I just love this game and I love what I do and I love the challenge of competing against such great players."

He will now be among the favourites at next month's US Open, the only major he needs to become the sixth player to complete the career Grand Slam. It is being held near his home in San Diego at Torrey Pines, a course he has won three titles on.

Ireland's Padraig Harrington and Shane Lowry finished in a tie for fourth at two under after closing rounds of 69.