Enjoyed a stellar amateur career, sparked when winning the Scottish Boys' Under-16 Championship in 2009 before backing that up a year later by claiming the Scottish Boys Championship. The Craigielaw player then landed a third national title by winning the Scottish Amateur Championship in 2012. He qualified for the Open Championship at Muirfield, where he played with former winner Mark O'Meara in the opening two rounds, in 2013, the same year he helped Europe win the Palmer Cup, the college equivalent of the Ryder Cup. During a spell at the University of San Diego, Forrest won four times, including the Redhawk Invitational at 2015 US Open venue Chambers Bay, where he shot sensational rounds of 63 and 65. In 2015, he won the St Andrews Links Trophy and also reached the final of the Amateur Championship at Carnoustie, performances that helped secure his place on the Great Britain & Ireland team that hammered the United States 16.5-9.5 at Royal Lytham. Forrest was also in the Scotland side that won the European Team Championship in Sweden last year and helped them retain the title in France in July. His swansong in the amateur game was also wearing Scotland colours as part of the three-man team that competed in the Eisenhower Trophy in Mexico in September.