Scottish wonderkid keeping the Andy Murray flame alive with thrilling run at US Open juniors

It is not only technical support that Robertson needs. While the Lawn Tennis Association keeps an eye on his progress, sending national coach Martin Weston to watch Wednesday’s win, it does not help him with his own coaching costs. He set up a GoFundMe page seven weeks ago which has so far raised £3,000 of his £15,000 target. Most of that was supplied by Scottish car dealership Arnold Clark.

One way of saving money has been to use his elder sister, Kirsty, as a coach. “Whatever she tells me, I’ll do it,” Robertson explained. “Because if not, she’ll tell my mum, and then I’ll get s— for it. She plays some Futures and stuff, and she works with Matt Little, so she’s really good on the physical side.

“If she doesn’t get her way, she’s pretty moody. When we’re at the dinner table, I’m like ‘I’ve had enough of tennis, let’s talk about something else.’ But I really enjoy it. We get on so well and so far we haven’t had any issues.”

From bucolic upbringing to buzz of Big Apple

Just like Andy Murray, who was thrilled to find himself billeted at the Hyatt Grand Central on his first junior trip to the US Open, Robertson is loving the noise and buzz of the big city – even if he admits that he could not cope with it for much more than a week.

He grew up on his father’s farm, which had to be sold up in order for the whole family to move to Stirling. They are still in the agriculture business, producing a variety of crops which – appropriately for a young tennis prospect – happen to include strawberries.

At this stage, Robertson’s limiting factor seems likely to be his size. He claims to be 5ft 8in tall, although that seems a generous figure when you meet him, But his technique looks extremely efficient, and thus far is helping to make up for his stature.

“Physically he has a lot of growing to do,” Judy Murray told Telegraph Sport, “but he has a great attitude and work ethic, as well as a huge desire to learn, which, to me, are the most important qualities. You can’t teach those”.