There is a fascin-ating passage in Richie McCaw's autobiography, where the All Blacks legend recalls the closing stages of his side's 2007 Rugby World Cup quarter-final against France in Cardiff.
Yannick Jauzion's 69th-minute try had given France a two-point lead, and there was a growing sense of desperation in the New Zealand ranks as the minutes ticked away. Time and again, McCaw's players set up positions for a drop goal, and time and again they bottled out of trying it. According to McCaw, going for the drop had never been part of their strategy; it just wasn't in their play book.
Just as well that Duncan Weir was better prepared. Going into last weekend's Six Nations clash with Italy, he and kicking coach Duncan Hodge had gone through a few routines, with Hodge whipping the ball back to the fly-half then trying to block his strike. When Weir turned an imminent 20-18 loss into a 21-20 win with his imperious kick in the Stadio Olimpico, Hodge deserved at least some of the credit.
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Not that you would want to take any gloss off Weir's achievement. The modest, self-contained 22-year-old is not one of life's natural history men, but his clinching effort in Rome eight days ago will be talked about in Scottish rugby circles for years to come. But if his nerveless bearing then suggested confidence, a casual remark a few days later suggested it wasn't particularly well-founded.
How often, he was asked, would he expect to nail such a kick in training? Weir thought for a few moments, then delivered his discomfiting reply. "It would probably be just over 50%," he said, nonchalantly. In which light, backing himself to nail one with a Test match on the line, around 50,000 fans willing him to miss, and with his place in the team at stake, showed a staggering level of assurance.
It is only a few weeks, after all, since Weir seemed in danger of being a Six Nations spectator. He had dropped down the playmakers' pecking order at Glasgow, where Ruaridh Jackson was being preferred for the big games, and new competition for the Scotland No 10 shirt was emerging, with Greig Tonks and Stuart Hogg making it clear they both fancied a crack at the job as well.
Yet in taking his place against Italy, Weir made his fourth consecutive start for Scotland, the longest run of his 11-Test career. As all but two of those seven previous caps had been won as a replacement, the change in his fortunes is quite startling. He is undoubtedly feeling the love of interim head coach Scott Johnson - but is he feeling any better for it?
"It's huge," Weir smiled. "As a 10, and on the learning curve over the Six Nations, it's huge."
But while the triumph in Rome last weekend will be seen by most as the making of Weir, his own view is that what happened in the England game at Murrayfield two weeks earlier was probably more significant.
"It's just the pressure of being in these situations," he said. "The team's not performing well, you are 20 points down and you're trying to generate some momentum. You have never been under pressure like that, especially at a full Murrayfield, and you feel that you're letting yourself down and letting the 70-odd thousand who are watching you down as well.
"You just want to learn. The coaching staff here are always striving to fine tune the detail of what you are putting in. It's a huge learning curve, about gaining experience and making sure days like the England game won't occur again."
This is the almost routine, analytical voice of the modern professional player - dissecting, deconstructing, building on experiences gained. But as cool as Weir was under unimaginable pressure in the moments building up to his winning kick, he was anything but that in the seconds afterwards. Even as referee Steve Walsh began to raise his arm to signal that the strike was good, Weir was racing back down the pitch in a fist-pumping eruption of joy.
"It's funny," he said, still a little embarrassed by his own reaction. "I have a picture on my wall from my first appearance as a pro for Glasgow. I kicked a drop goal that day, too, and it shows me doing the same fist pump I did at the weekend. It's a nice photo to replicate in a Scotland jersey.
"It's the stuff you dream of as a kid, scoring a try or a penalty or a drop goal to win a match for Scotland. It was an immense feeling. Hopefully, we can build upon it as a team and take on France in our own backyard next weekend."
After the England game, Weir had talked about his embarrassment at being spotted in the supermarket. After Italy, with his status as a national hero duly cemented, he might have been tempted to volunteer for a shift on the tills. It was never going to happen, though. Wallowing in adulation just isn't his style.
Weir said: "After a win you obviously do feel a wee bit better. You've got the chest upright and you're not hiding away. But I wouldn't say it is puffed out any more than usual.
"I know there is going to be a lot of learning coming out of that game when I do the review with the coaches. It's about learning what you have to do. Although you have knocked over a drop goal there are still another 78 minutes in the game to think about."
Weir will have a few other things to consider in the weeks ahead as well. His contract with Glasgow is up at the end of this season, and his desire to stay is unlikely to have been enhanced by his intermittent pattern of selection at the club. At the same time, what he did in Rome last weekend will have done a lot to raise his profile, and his price tag, for clubs outside Scotland.
But for the moment, the player who turned his back on a promising football career - he was on the books at Celtic for a time - can just enjoy the fact that his decision to opt for rugby has been vindicated.
"I had the option to stay on at Celtic, but I just decided to leave," he said. "At that stage, I just wanted to give rugby my full attention and see where it would take me."
Contrary to legend, not all roads lead to Rome. But Duncan Weir's certainly did.