'I'm not just going to Glasgow for the kilt, I want to try to win'

The past few days, then, should have been among the most joyous of the teenage discus thrower's young life, a time during which he should have been overwhelmed by the congratulations of friends, family and colleagues. Instead, though, he has been rendered almost mute by crippling fear. Not fear of failure or of the competition, but fear that the news of his selection would leak out before the first raft of Team Scotland athletes were announced yesterday. Indeed, despite having already received permission to discuss the news ahead of the embargo, Percy's wariness even infected the first few minutes of this interview.

"Not even my coach knows," he conceded conspiratorially on Monday night. "The only people who know are my parents, my sister Brogan, scottishathletics and Commonwealth Games Scotland and it's been absolutely tearing me apart that I can't tell all those who have helped me over the past few years. I don't want to risk saying it to one person and get a phone call saying I'm kicked off the team for announcing it too early. I've been sitting in the corner quietly at school for the past few days wanting to scream it out but I can't."

The words gushed out in a torrent, propelled by days of pent-up excitement, but now the secret is finally out and Percy can spend the next 300 days impressing himself upon an uninformed Scottish public before the Games begin. After all, he remains something of an unknown quantity given the abrupt nature of his emergence over the past few weeks.

A silver medalist at the European under-20s in July, he threw the heavier, senior discus - 2kg rather than the 1.75kg implement used by juniors - for the first time this season, and only the second time ever competitively, at the Scottish Championships last month, winning the title ahead of favourite Angus McInroy with a distance just 16cm short of the qualifying standard for Glasgow. Success in the discus, shot and hammer at the Scottish under-20s followed before the teenager returned to senior competition and recorded the required mark of 56m twice inside 24 hours. All this in the space of little more than a month.

"It's all catching up on me now," admitted Percy, who is ranked in the world's top five at age-group level. "It's been a shock getting it this early because I didn't think I'd get the qualifying this year. I did one competition in 2012 with the 2kg and struggled to break 50m, but this year I fouled a 58m. I don't have the consistency just yet because I've not done that much training with it but, with a full winter behind me, the security of knowing I am in the team, and a little bit more maturity, I think I can really kick on next year even if it's still weird to think I could be at a competition with Usain Bolt and in a team with people like Eilidh Child and Eilish McColgan who have been to World Championships."

His accent will sit strangely, too. Percy was born in Glasgow, and his parents lived in the city for 15 years, before the family relocated to the Isle of Wight when he was five. Yet despite spending much of his life in England, he considers himself Scottish and cannot wait to walk out at Celtic Park for the opening ceremony wearing a kilt. "I'm not just going for the kilt, though. I'm going to try and win," he insisted. "My first aim is to try and get into the final because so many of the world's top 10 will be there but I just don't know how much I'll develop and how the competition will develop over the next year. I could break 60m and get a medal or break 60m and finish sixth."

Should he fail to meet his own high standards, it will not be because of a lack of effort. Percy suggests that his rapid progress is simply a consequence of getting "bigger and uglier" but such self-deprecation masks a ferocious work ethic, one which manifests itself in the remarkable dedication he demonstrates to simply attend throwing sessions.

In order to work with John Hiller, who coached Lawrence Okoye at the last Olympics, Percy leaves home at around 5am to travel to south-east London and, depending on the traffic and ferry crossings, is often not back in the Isle of Wight until 9pm. This gruelling journey, accompanied either by father Andrew or mother Deborah, is completed two or three times every week. "The irony is my local gym is a 30 second walk away from the house," he said. "But I either sleep or do my schoolwork during the journey and that's my life - throwing, lifting, schoolwork and sleeping - but I enjoy it. I'm on a two-week break just now but will go for a few runs, which I despise, but I know If I don't, one of my rivals will and I don't want to give anyone else an opportunity to beat me."

His early selection should allow ample opportunity to hone his training programme and perhaps even strive for the qualifying mark in the hammer, albeit Scotland's strength in the discipline makes a dual selection unlikely.

Still, Percy has developed a habit of achieving the unexpected and who is to say his development will not be accelerated further over the coming few months? After all, discus is a notoriously volatile discipline. Australian Julian Wruck is the early favourite for Glasgow but his performances dipped dramatically after gaining somewhere in the region of 35kg over the winter and he could only finish 11th at the World Championships in Moscow.

Such stories make Percy, often the smallest in whichever field he competes, wary of bulking up too much, too soon, but that does not stop him consuming "a full melon, a full pineapple and about 10 or 11 different kinds of fruit" in smoothie form every morning. "If I wanted to, I could put on a few stone in a few weeks but I want to add the right kind of weight - muscle rather than fat," he said. "I'm in no rush. I don't want to force putting on weight and compromise my performance; technique and speed are just as important if I want to get a medal for Scotland next summer."

The job is not quite done yet . . .