Calum cut his golfing teeth at Aberdour and Muckhart, winning a couple of Perth & Kinross county events when he played mainly at the latter, but came through the amateur ranks in the shadow of players like Bradley Neil and Josh Jamieson.
He followed a fellow Aberdour member and former Scottish internationalist, Scott Crichton, to Western New Mexico University, using his spell in Silver City to not only improve his game but also make a big impression as a person.
“Calum is a bit of a folk hero at Western New Mexico University because of his golf, but more importantly, he’s just a wonderful young man,” said the man who was his coach there, Kent Beatty.
After graduating with an accountancy degree, Calum stayed on to be the men’s assistant golf coach with the ‘Mustangs’ and during that two-year spell he secured a Masters in Business Administration (MBA).
He turned professional in April 2017, dipping his toe by playing in the odd tournament, before wasting no time making his mark as he was able to play a bit more in the summer break.
He shot rounds of 66-67-65-65 for a 21-under-par total – the fifth lowest in the event’s 53-year history – to win the San Juan Open by nine shots, joining two fellow Scots, Martin Laird and Jimmy Gunn, in landing that prize.
Calum then backed that up with an equally impressive performance to win the Arizona Open Championship, finishing four shots clear of that field at Troon Country Club in Scottsdale with a 10-under-par 200 total.
Those two triumphs convinced Calum that he should be pursuing a player career and things have continued to go from strength to strength for him in 2018.
He came through two qualifying stages, sharing top spot in a sectional event at Canoe Brook Country Club in Summit, New Jersey, to earn his major debut in the US Open at Shinnecock Hills.
Calum fired opening rounds of 75-69 to make the cut along with Scottish No 1 Russell Knox before ending up 61st behind winner Brooks Koepka in one of the toughest course set ups in major history.
Then, in just his fifth start on the Challenge Tour, Calum won the Northern Ireland Open at Galgorm Castle, closing with a seven-under-par 64 for a 19-under-par 265 total.
Calum went on to make the Grand Final in Ras Al Khaimah at the first attempt, finishing 35th on the 2018 Challenge Tour Order of Merit despite playing in just 12 tournaments.
His 2019 campaign came alive after giving an excellent account on his European Tour debut when recording a top-30 finish in the Aberdeen Standard Investments Scottish Open at The Renaissance Club.
Calum shot rounds of 65-64-67-66 to win the Euram Bank Open in Austria with an 18-under-par total at Adamstal Golf Club before backing that up with third place in his next outing in the Vierumaki Finnish Challenge.
Riding on the crest of a wave, he then won the Made in Denmark Challenge – Presented by FREJA by carding scores of 67-68-64-67 for a 22-under-par total at Silkeborg Ry Golfklub before adding two more top-10 finishes in the ISPS Handa World Invitational Presented by Modest! Golf Management in Northern Ireland and the Rolex Trophy in Switzerland.
The blistering run of form lifted Calum to the summit of the Challenge Tour Order of Merit and, impressively, secured his European Tour card for the 2020 campaign with nine events to spare.