Andy Murray and Brad Gilbert, the odd couple of British sport, are out on court at the Nick Bollettieri Tennis Academy in western Florida. The weather is not conducive to strenuous exercise — a temperature in the mid-80s and humidity so oppressive it seems to suck the oxygen from one’s lungs — but they have been doing their thing for more than 90 minutes.

Gilbert is watching from the edge of the court in trademark posture: arms folded, back straight, his wraparound shades concealing any thoughts he may have as he watches his young charge play the full repertoire of shots in preparation for the ATP event in Washington next week, Murray’s first competitive outing since injuring his right wrist ten weeks ago. Other than the odd word of encouragement, the American seems content to let Murray find his own way.

Murray, for his part, goes about his business with an air of mild disgust for his profession, the occasional expletive escaping his parched lips as he does battle with the hellish conditions. His hitting partner — Michael McClune, a 17-year-old from California — is also feeling it. Two days previously McClune vomited — loudly and liberally — at the end of the morning session. This is the daily grind of professional tennis, the life that Murray and Gilbert have shared for 12 months.

By any reckoning it is one of sport’s more unlikely coach-player relationships: Gilbert, the straight-talking, sharp-shooting obsessive who has had to learn the art of quiet diplomacy to coax the best from his waspish charge, and Murray, the 20-year-old wunderkind with the sharp mind and sharper tongue who is not afraid to use crimson language when he disagrees with Gilbert but who has come to respect the American’s tactical nous and all-round dedication.

One year after being manacled together with the help of a sizeable cheque from the LTA, the Oscar and Felix of the tennis world are still talking and the relationship is still working. “Brad steers clear of the technical stuff and allows me to express myself with the shots I have developed over the years,” Murray says after slumping down at the conclusion of the session.

“But he is tactically brilliant. He takes the time to scout opponents and watch videos so we can come up with the right strategy for each one. He has made a big difference, which is great because I would not have been able to afford him without the help of the LTA.” But does Murray wear the trousers in the relationship? “It is important that a player knows his own mind and takes ownership of his programme,” the British No 1 says. “I am not the kind of person who will just follow instructions without getting involved.”

A couple of days earlier, in the weights room of the academy, Gilbert had offered his thoughts on his turbulent protégé. “There is no magic pill, no guarantees, I just try my ass off to get Andy to be as good as he can get,” he said. “But it helps a lot that Andy is someone with bags of talent.”

But how does Gilbert cope when he gets a verbal lashing, as often happens when Murray loses his rag during matches? “It’s not a personal thing,” Gilbert said. “It’s more a personal thing to himself that he is not doing better. He’s just venting. I would never have done it to my coach and Andre \ would not have done it to me. But that’s the thing: everyone is different and you have to handle what comes your way. I don’t think it’s good if he does it day in, day out. But that’s his release a little bit.” Is it something that is diminishing over time? “I hope so,” he said, laughing.

Many have sought to unpick the Murray psyche, but one comment during our courtside conversation is particularly revelatory. For some reason we have got on to Harry Potter and the Scot confesses an interest.

“I went out and bought the latest book because people had been speculating that he might be killed off, which I thought was ridiculous,” he says. “I just read the last three pages to find out. It told me everything I needed to know.”

That is Murray in a nutshell: a young man in a hurry, a no-nonsense 20-year-old who cannot be doing with anything that does not get him to his intended destination in the fastest time possible. This is not someone who is likely to spend his spare moments pondering metaphysics or the finer points of Shakespeare.

“Let’s cut to the chase,” is what his dour expression is telling us. “Don’t give me the runaround.” And that is his charm. When you meet him you get the real deal, the uncut version, not the confection of some slick PR agent in the background, pulling the strings. In an age of spin and subtle deception, it is gloriously refreshing. If only he could smile more — something he began to do as he loosened up — he may even become endearing.

He begins to open up about the trials of life on the road, particularly in the context of his blossoming relationship with Kim Sears, the daughter of Nigel, a British tennis coach. “We have been together for about 19 months now,” Murray says. “She starts university in a month or so. Of course it is difficult because I am away such a lot, but if you like someone a lot it can work out. The same goes for my friends and family. Because I don’t see them that much, the time I do spend with them is that bit more valuable.

“I don’t get the chance to spend six weeks at a time with my family or girlfriend, but maybe when I get the odd week or two it means that I am really happy to be with them. Whereas if you are with them all the time, I guess you might argue and get angry with each other.”

The key to Murray’s sporting progress — and, by implication, the progress of British tennis — is staying injury-free, so it was a decision of considerable maturity to miss Wimbledon to allow his damaged wrist to recover, a process that is nearing completion. Indeed, the break from competition may assist Murray as he begins the countdown to next month’s US Open.

“I have improved my core fitness over the last ten weeks, which should hold me in good stead over the next month,” he says. “The hard thing about the American tournaments is that the courts get so hot. You can feel it through the soles of your trainers and it makes your legs really burn. That gets you even more than the heat in the air.”

Murray pulls himself off his chair to hook up again with Gilbert and stretch his weary muscles. Afterwards they will take lunch and get ready for a further hour of tennis in the late afternoon before another weight-training session. I wish him luck and he grimaces, an expression that slowly turns into a smile. One is struck with optimism that, as he matures, his relationship with the British public may become one of mutual warmth.

A few minutes later he emerges from the gym with Gilbert, the two men loping slowly off in each other’s company, respectful of each other but wary, too, like a wasp and a scorpion. One suspects that they will not be pen-pals after their association ends, but it is a relationship that, so far at least, is working wonders.

Life on the road

Andy Murray on the scourge of the wrist

— It is getting better. I have been training hard for ten days on the court, but I have also been training hard off it for eight weeks now. I still can’t hit full on the forehand, but each day I am trying to strike it a little bit harder and not rush it. Hopefully by the end of the weekend I should be fully fit.

— The break from competition has probably done me some good. You can get match-fit by playing loads of matches, but you are not really getting physically stronger. When you get the chance to concentrate specifically on building up fitness, it gives you an advantage on the other players who have not had the opportunity to do it.

— Some days I find it difficult to get up for the running, but it helps having Brad [Gilbert, his coach] around to motivate you.