The Olympic tipping point
Everyone who competes at an Olympic Games must have shared the same moment of realisation at some point in their career: "I can do this. I am good enough to reach the Olympics."
If you don't have that moment, you can't commit to it - and most sports demand years of commitment to stand the remotest chance of Olympic participation.
What is that moment like? How does it feel to realise you might have what it takes? When do you start sacrificing things to pursue that dream?
I've had the privilege of meeting one family in the same week that this moment struck their teenage son.
Marsh won a junior world title from a ranking of 140th
The 16-year-old had entered the competition, held in Jordan, ranked 140th in the world for the age group. Marsh was almost rock-bottom of the pile when the draw was made.
But, watched by his parents back in Wiltshire using simple score updates on the tournament website, Marsh threw his ranking out of the window on the way to the world title, defeating the defending champion in the process.
"I didn't have any pressure," Marsh told me. "I had no expectations and nobody else expected me to get anywhere. I relaxed more than I've ever done and enjoyed fencing more than ever before."
It's very hard to accidentally win a world title at any level, but I had to ask: given his ranking, did he think he'd fluked his way to it?
"Yeah! When I first did it, I couldn't believe what had happened and I don't think anyone else could either. I was looking back at it thinking that I must have had an easy fight, or maybe everyone I fenced had a bad day.
"But now [a week later] I'm beginning to realise actually they were all fencing quite well - so it must have been me fencing well, too. Maybe it was a fluke, but I feel like I could produce a result like that again in near future."
This is good, because world champions are expected to produce results and junior gold medallists are expected to work their way into the senior ranks. That's a scary prospect when, at the start of the day, your future plans extended no further than thoughts of a medical degree.
"Before, when people asked me where I wanted to go with fencing, I'd light-heartedly say I might go to Rio 2016 if I'm lucky," said Marsh.
"But now I've done this, 2016 doesn't seem as far away. Before, it seemed like something I could say and then forget about it; it wouldn't really happen. Now, if I work hard enough and get the right results, I really can get there. It's an opportunity for me to take.
"As fencers go, I didn't train that much. Now I've done this, our coach has got more training planned for me and everyone will be expecting me to train a lot harder.
"I still want to do medicine at university but it's going to be hard to balance that with fencing. Overall, medicine is more important to me than fencing. But, in the short term, fencing will take a more dominant role."
Philip's parents are Tim, an airline pilot, and Penny, whose days are spent steering their three children between school and sporting events. The two already go for days without seeing each other - Tim arriving home from a night flight as Penny bundles the kids into the car for a drive to Sheffield - so the sudden emergence of a world champion in the family requires careful consideration.
"We recognised he had a talent and that he was improving," says Tim, "but I never dreamed he'd reach this level this year.
"We'll have to think long and hard about how we take the next few years. At 140th in the world, it's difficult to justify devoting too much time to the sport. But with this, we'll have to think quite carefully."
Their son has had a remarkable five years, having dislocated his hip playing rugby for his local team at the age of 11. "They were talking about replacing his hip," remembers Tim. "And you think, 'replacing his hip? He's 11.'"
Even now, the hip is held together with metal plates (though Philip says he barely ever feels it). It isn't a traditional recipe for a budding Olympian, but his parents know Philip has now proved he has more chance than your average sporting child.
"It's going into the unknown - an exciting unknown," says Penny. "This is all so new to us. There's a lot of talking to do in the future but we're behind him and we'll support him in whatever he wants."
Tim adds: "And there's a difference between U-20s and the adult scene. A junior title is no guarantee at all. The Olympics is very much a goal, rather than 'he's going to make it'.
"When he was growing up, we didn't want to be pushy parents. You don't want to stitch your child up.
"Now, it's quite surreal. All we can do is support him as best we can."
Penny concludes: "Five years ago, when he dislocated his hip, we were in such a dark place. We've come a long way in such a short space of time."
How much further their son goes now depends on the choices he and they make. That is a daunting prospect: fencing, of all sports, won't pay any bills unless you are the very best of the best, so you have to be sure of yourself before committing. Medicine, by contrast, is a degree geared towards a healthy and regular income.
If you were Philip or a parent faced with the same situation in your sport of choice, how would you play it?