Lee Byrne stepped cautiously on to the new Wales team bus. It could have been the ankle he turned against Perpignan, while on Heineken Cup duty for the Ospreys, but it could just have been wariness. The team bus is supposed to be a bit of a sanctuary; travelling in it through the streets of Cardiff to the Millennium Stadium on match day is one of the special journeys in a rugby player's life.

But here it was, parked up at the Vale of Glamorgan hotel and serving as an interview room. He eased his 6ft 3in frame into a front seat – taking up more room than your conventional back-three player – and settled into the slight frown that seems to be his everyday facial wear. He is said to be a sensitive soul who worries about his form, about what people might think of his performances.

I must say I have seen him in more carefree mood, when the frown gave way to a right little sparkle. It was after the BBC Sports Personality of the Year show, where Wales's 2008 grand slam had been toasted, and the team were relaxing.

"Good night, wasn't it?" Byrne says. He put his serious face back on. "Not many of those now."

One of the interesting things about Byrne is that he is a late developer. He is 28 and absolutely world class at full-back, but was not capped until November 2005 and did not earn that special tag until last season in the Six Nations. In fact, he had been left out of the Wales 2007 World Cup squad. Had Gareth Jenkins, the coach at the time, explained to him why he had missed out?

"Not really. They wanted to play Gareth Thomas at full-back and then went for Kevin Morgan. Fair enough. I was disappointed, of course. But what would they have told me? I talked to a couple of people about it, but, really, anything I had to do to get my place back had to come from me."

He is from the rugby hotbed of Bridgend, the town 20 miles west of Cardiff that has produced more than its fair share of top players. Rob Howley and Scott Gibbs and Gareth Thomas. Bridgend boys. Another, Gavin Henson, is from nearby Pencoed, son of a first-class hooker, Alan, who captained Maesteg up the road. Henson was a teenage prodigy, making the headlines then and never out of them since.

Byrne's father, Martin, is from Consett in the north-east of England. He met Byrne's mother, Lynne, in Jersey, before settling in her home town. Lee went not to the famous rugby school of Pencoed but to Archbishop McGrath Catholic School in Ynyswadre, just to the north of Bridgend. He started to play club rugby with Bridgend Athletic, then Tondu, before being recommended by that club's coach and former Wales prop, Huw Williams Jones, to Nigel Davies, then assistant coach to Gareth Jenkins at Llanelli.

"I had a trial with Llanelli just before the regions were set up. I won a regional contract with the Scarlets, but it didn't really happen for me there. So, I joined the Ospreys."

And ... and? What happened to Byrne that changed his life, from that journeyman full-back going slowly up his career path, to this streamlined interstellar projectile? "I don't know. I honestly don't know."

Something must have happened. "I know. I do worry about the way I play. Or played. OK, I feel different now. I suppose it's all about confidence."

There was no defining moment, no high ball that he plucked out of the air. But a lot of people put in a lot of little bits. "Lyn Jones [the former coach of the Ospreys, who has just accepted a coaching job in Abu Dhabi] was good to me. So are the current coaches under Sean Holley. But I also learned a lot from Ian Foster, the Waikato coach, who's done two short stints with us at the Ospreys. And then, of course, there's Shaun Edwards with Wales ..."

What does Edwards tell him, or sell to him: the bigger picture or the detail? "Well, both I suppose. Shaun told me all about how he got over disappointment. But the detail is the thing. Wait, wait, don't rush into the line. Pick the angle and trust your instinct."

The current Byrne trademark is to catch a high ball, run, kick, chase, jump and regather. It is as electrifying as Shane Williams in full flight, because it not only does damage to the opposition in its own right, but also delivers the message to opposing playmakers that they had better think twice about kicking to the Wales back three. Because if Byrne does not run he will kick, with a booming left boot, as long as Henson's right.

There is also his judgment of angles and the timing of his runs. For a full year under Warren Gatland, Wales have been probing at theory, working on the breakdown of organised defences. It is about speed of initial delivery, then the strength of the burst over the gain line, then the stretching of the defensive line before launching the dodgers and darters at more heavily planted tacklers.

And then the offload to the finishers, among them the full-back who has to have his sums on speed and direction all worked out in a fraction of a second. When it is working smoothly it is as easy on the eye as rugby can be, and Byrne, diving with one hand exerting downward pressure on the ball and the other raising a finger to the sky is the master of his craft. With not a crease on his brow, not a doubt in his mind. He may have taken his time reaching this point but he is enjoying every moment of it.