Locke carded a seven-under-par 65 for the second day running to land his second victory on the Tartan Pro Tour by three shots, having been completely unaware that local man McDonald had held the lead with seven holes to play.
That position changed as Locke, who won the Silver Medal as leading amateur in the 2018 Open at Carnoustie, covered the closing stretch in a blistering five-under, signing off with four straight birdies.
The 22-year-old’s 14-under-par total represented one of the outstanding performances in the circuit’s short history, with the 2021 campaign having started with a bang after Gavin Hay carded a second-round 64 in winning the Montrose Links Classic last week.
“I am chuffed with myself,” admitted Locke, who is managed and mentored by the tour’s founder, Paul Lawrie.
“The key over the last couple of days was that I drove it very well yesterday and, though not as well today, it was still okay and my wedge play was a bit better than yesterday.
“To be honest, I didn’t look at a leaderboard until the 17th tee, so I had no idea what was going on with Jack or anyone else. I like to play my own game, if I can play the best I can, what will be will be.
“I had a look on the 17th tee and would probably have taken an iron off the tee there if I was leading by a few shots, but I went with driver then hit two of my best wedge shots all week there and the 18th.
“I hit it to six feet at both holes, having hit a driver and 9-iron to 12 feet at the par-5 16th and had no idea how my eagle putt missed. I was pretty proud how I finished today, to be honest.”
McDonald, an honorary member of Barassie along with fellow Walker Cup players Jim Milligan and Gordon Sherry, carded scores of 67-66 to take second spot by three shots from fellow Ayrshireman Michael Stewart (69-67).
However, this was another sparkling performance from Locke, who certainly has the game to make his mark on the Challenge Tour and, eventually, the European Tour as well..
“Any win is great and I think I am learning how to win,” he added of a success worth £4,100. “My game is better than it was last year and that is pleasing.
“I just concentrate on my own game and, if I can keep shooting scores like I have this week, then I will be tough to beat.
“I am playing in the next two Tartan Pro Tour events then the PGA EuroPro Tour starts at the end of May.”
The Tartan Pro Tour now heads north for the Royal Dornoch Masters at the beginning of next week.
“It’s a great wee tour,” said Locke of the circuit set up by Lawrie to provide playing opportunities for home-based players in the Covid-19 world last year and now boasting 12 events this season.
“The competition is good and we are thankful to be competing again and getting the juices flowing again.”