THE glowering skies over Troon were regularly pierced yesterday by a shaft of light ultimately sourced to a set of white-walled gnashers located in the frame of Phil Mickelson.

His sunny demeanour as he constructed a fine 69 to retain his lead at The Open may not quite have lifted the dankness hanging over a sodden course and its patrons but it did serve to illustrate the truth that good scores can be found in any conditions and that easy smiles can follow hard work.

“This is where it kind of turned for me,” said Mickelson, referring to 2004 at Troon where he finally mastered the art of links golf, finishing just one shot off a play-off for the claret jug after years of failing badly on links courses. “This is where it kind of happened. This is where I stopped trying to overpower the golf course, where I accepted playing it as it is designed.”

This philosophy, combined with alterations on applying spin to the ball, saw Mickelson compile a total of 10 under. It was just enough to keep him ahead of Henrik Stenson, Soren Kjeldsen and a posse of Mickelson’s compatriots, emphasising Troon’s reputation as a course that puts down a particular welcome mat for American golfers with the past six Open champions here being from the US.

Mickelson’s closest pursuers, though, were the Scandinavians. Stenson of Sweden shot 65, the best round of the day, to finish one behind the American. Kjeldsen of Denmark fired a 68 that left him three shots off the lead.

The three not only shared excellent scoring in a morning of unremitting rain but they are also members of the over-40 club: Stenson is 40, and Kjeldsen is 41 while Mickelson, at 46, is bidding to be the oldest winner of The Open for 150 years.

The American, a winner of five majors, is certainly not talking his chances down. “I have already won The Open and that takes a lot of pressure off me,” he said, adding he was better physically than 10 years ago.

He was typically bright and positive about the weather, saying he loved to play in the rain in his childhood home of San Diego. “We got maybe three days like this a year and on those days there was nobody on the golf course. So those are my favourite times.”

Kjeldsen, whose upbringing in Aarhus was slightly wetter, said of his childhood days: “I am used to playing in bad weather. You did not stay inside because you would miss too many days.” His battle has been with himself rather than conditions. He said: “I was struggling for a couple of years. I found it really, really hard.”

At 5ft 7in, Kjeldsen is not one of the modern monsters who can crack the ball 350 yards. “I am 41 and I hit it 280 yards and I try to make the most out of it,” he said. “I do not feel intimidated by anyone. I think I have won the battle within and I think that was a tougher battle to win than against any other player.”

The Scots had a dreich to dismal day. Russell Knox, on level par, was the leader of the Caledonian clan and the projected cut had Colin Montgomerie and Paul Lawrie both playing at the weekend on +4. Richie Ramsay at +5 plus just missed out, with Marc Warren, at +11, and Sandy Lyle, at +21, never sweating on their fate.

Other famous names also had to make premature travel plans. Ernie Els, a past champion, Shane Lowry and Louis Oosthuizen saw their dreams evaporate on soggy Troon. The indignity was overwhelming for Oosthuizen, an Open winner in 2010, whose first-day hole-in-one must have seemed a long way away when he carded a nine at the 11th en route to an 83. Other pre-tournament favourites were off the pace with Jason Day, world No 1, finishing 11 shots behind Mickelson and Rory McIlroy and Dustin Johnson sitting eight shots off the lead.

The Northern Irishman already has won four majors at 27 but is aware that he has considerable strides to make to contest the 145th Open. But he said: “I feel like it is possible. There are 36 holes to go. Obviously the guys at the top of the leaderboard are playing very well — but I have given people head starts before and been able to win.”

The postscript to a rainy day goes to Jordan Spieth, a winner of two majors at 22, who shot a 75 to make the cut with nothing to spare.

“You wish your score did not matter when you play in this. You wish this was just a round with your buddies where you go into the clubhouse and have one or seven pints afterwards,” he said — en route, one presumes, to the bar.