In mountaineering, there comes a point during the ascent of the world’s tallest peaks where climbers enter what is ominously called the Death Zone.

At dizzying altitude, this precarious environment is the point at which the pressure of oxygen is insufficient to sustain human life for an extended period. There are few places on earth where time is more finite, or the physical impact of scaling the highest heights so profoundly obvious – it is not a place where one outstays their welcome.

I found myself thinking about the Death Zone on the Sunday of the PGA Championship as Phil Mickelson – one of the greatest golfers of his generation but one who was also moving into the twilight of his career – beat the odds and became the oldest ever winner of a major tournament at the ripe old age of 50 years and 11 months.

Elite sport for the most part is a young man’s game. It requires its athletes to be in peak condition or have their weaknesses unmercifully exposed by the opposition. Time, however, is an unavoidable adversary, and as it marches on, the physical and mental scar tissue of what the very best are forced to endure reveals itself with increasing regularity.

Much like the mountaineers setting out in pursuit of the summit, there’s only so long you can spend on top of the world before it’s time to come down. Make no mistake, Mickelson has climbed the highest mountains, but for the last few years he’s been on the descent.

His last PGA Tour victory came at the Pebble Beach Pro-AM against a depleted field, while he hadn’t won a major since the 2013 Open. His last couple of seasons have been punctuated by wildly erratic displays with the driver (he ranks 181st on Tour for strokes gained off the tee), while his famously magic short game has failed to remedy the fact he’s making far too many mistakes during an average round.

Mickelson has climbed the highest mountains, but for the last few years he’s been on the descent

In the meantime, he’s become something of a walking satire: his tongue-in-cheek “Phirside with Phil” videos where he reminisces on days gone by, his ludicrous dancing TV advert for Mizzen and Main, he’s set up a coffee brand called Coffee For Wellness, and the ever-so slightly cringe viewing of his one-on-one The Match and The Match II against Tiger Woods. None of it is mean-spirited or intended to be anything other than a bit of fun, but it's symptomatic of a golfer finding alternative avenues for amusement outside of world-class golf.

Entering PGA Championship week, he had fallen to 115th in the world rankings having missed six cuts this season and failing to finish inside the top-20 on any of his appearances. With odds ranging from 200/1 to 500/1 for the tournament, Mickelson was expected to turn up at the incredibly testing Kiawah Island Ocean Course, be a momentary sideshow before the “real” golf started, and then pack his bags on Friday having missed the cut. But they don’t call Mickelson “Phil The Thrill” for nothing.

What transpired was four days of simply breathtaking golf. With winds gusting to 25mph and the course playing a remorseless 7,800+ yards (the longest major in history), Mickelson toughed it out as many of his younger competitors followed – some of whom, including Justin Thomas, Xander Schauffele, and world number one Dustin Johnson, failing to make the cut at all – before gutsily staring down the tough Brooks Koepka on Sunday to claim the sixth and most significant major of his career.

Contrary to the all-at-sea golfer we’ve witnessed in recent times, the San Diego native was in complete command of his game throughout the week. He led the field in strokes gained tee to green (encompassing driving and approach to the green), putted imperiously when the pressure was on, and of course the wedge game was magnificent when it needed to be – he holed out from the sandy area on the par-3 5th to wrestle back the lead, and was greeted with an incredible ovation.

Fans have waited almost two years to return to the golf course and, here, thousands of them were greeted to one of the vintage major performances of the modern era. As Mickelson made his way up to the 18th green, the rapturous fans chased him down the fairway – following the Pied Piper as he played his merry tune. So soon after Tiger Woods completed his impossible return to the winner’s circle, it’s only right that his most fierce rival should seek to gazump him; the irony, I’m sure, is not lost on either man.

As Mickelson gave his champion's speech next to his newly claimed Wanamaker Trophy, it's notable that Leftie didn't seem overly emotional. There were no screams of euphoria or tears being held back behind glassy eyes. Just a wry smile. Against all the odds, Mickelson had turned around in the Death Zone, and summited the mountain once more. Maybe he was just admiring the view from the top.