A year ago next week, Joe Salisbury was playing in the County Cup - a much loved but essentially dog-eared event, staged in Bromley, in front of an audience of a few dozen people. Quite a contrast, then, to the 17,500 who will fill the O2 Arena on Sunday, as Salisbury makes his debut at the ATP Finals.
Tall and skinny, with the studious air of the kid who always delivered his homework on time, Salisbury has not yet adjusted to his newfound eminence.
He and his American doubles partner, Rajeev Ram, each collected a decent pay packet of around £400,000 this season, and yet Salisbury - who turned 27 in April - still lives in a flat in Peckham with his sister and her boyfriend. In an interview with The Sunday Telegraph, he sounded like a man counting his blessings.
"It is unbelievable, to play here in London," Salisbury said. "I have always loved watching it on TV, and I have usually come to see it in person for at least a day every year. But I never even been close to qualifying before this season.
"It's such a special event, especially for doubles players because it gets equal billing with the singles. Every match is on Centre Court and on TV, whereas even at the grand slams you play most of the tournament on the outside courts and the final doesn't usually fill the stadium.
"It's a shame that we won't be at the O2 for much longer [the ATP Finals will switch to Turin in 2021], because I think it has worked really well there.The crowds and support have been great. Hopefully, Rajeev and I can leave a mark this week."
The ATP Finals involve the top eight singles players and doubles teams of 2019, according to points accrued over the season. At least one Murray brother has been present for every edition of the tournament since 2013, but Andy is still on his way back from serious hip surgery - and stands at No 127 in the world - while Jamie changed partner after Wimbledon, which meant starting from scratch in the rankings.
Salisbury thus finds himself flying the British flag on his own this week.
The late flowering of his career can be traced back to the autumn of 2016, when he finally made the painful decision to abandon his singles ambitions. He had won a Futures tournament in Sweden the previous year, beating hotly tipped teenager Mikael Ymer in the final. But when those points dropped off his record, he fell out of the world's top 1,000.
"It wasn't an easy call to make," he says, "but it was forced upon me by some of the health issues that I've had. Chronic fatigue, glandular fever when I was younger. I would have liked to see where my singles could have gone but I don't think I ever could have got to the top level.
"If I did too much, especially if it was for a few weeks in a row, either training or tournaments, then I would feel completely wiped out, no energy, like how I felt when I had glandular fever. Doubles is so much less physical. Yes, you have to be agile, quick and explosive. But in terms of endurance - of having to play long points and come back and do it again and again - it's nowhere near."
Salisbury grew up hitting balls at the Roehampton Club in south-west London, just a few hundred yards from the offices of the Lawn Tennis Association. His father was a copywriter and editor, his mother dabbled in coaching, and his two elder siblings also played to a decent standard.
Family holidays often took them to Cornwall, where he became a handy surfer.
He took the most sensible path for a talented but not world-beating teenage player, collecting a tennis scholarship to an American university. "I read business economics at Memphis. I was always fairly academic, so I definitely took the work more seriously than some others on the tennis team. I thought I might want to get into finance, but as time has gone on that has appealed to me less. Hopefully I will stay playing for a long time, and then I'd like to stay in tennis in some way, possibly coaching.
"This has been my first full year on the tour. Until 18 months ago, I was playing Challengers, then I made it to the semi-finals of Wimbledon with Freddie Nielsen [which more than halved his ranking from 81 to 40].
"It's a great lifestyle. We're doing what we love doing and we're travelling all over the world in what I guess are pretty luxurious places and we are looked after well.
"But it's also tough being away so much. I broke up with my girlfriend last month after about a year together. It was a long-distance relationship - she was American. It's hard to keep something going even when your girlfriend or wife lives in the same place as you. The travel does take its toll.
"I am not complaining, though. The doubles is not as prestigious as the singles, and I doubt that it ever will be. But for me, it's pretty amazing to be playing these big tournaments - the slams, the ATP Finals. I think it's rightfully being recognised that even if the doubles isn't up there with the singles, it's an important part of the tournament, an important part of the tour, and most people love watching it."