I've been thinking a lot about amadou these past few days.

Now, on the basis that most people have never even heard of the stuff, I suspect I'm in a pretty small minority in this train of thought, so perhaps I should explain.

Amadou is the thin layer of dense flesh found just beneath the skin of the Fomes fomentarius bracket fungus. It is a remarkable and rather precious material, particularly valued by anglers who use it for drying their flies. For the avoidance of doubt, we are talking about their fishing flies here.

Helpfully, Fomes fomentarius, also known as horse hoof fungus, really does grow on trees. However, finding one is just the start of the process. The next part involves cutting out the amadou layer and then simmering it in stale urine for three days. Just to inject an element of fun, it also has to be removed from the liquid and beaten flat with a blunt instrument from time to time.

Fascinating stuff, but by far the most intriguing part of it all is the question of how this discovery came to light. After all, there is something rather counter-intuitive about creating a drying agent by immersing it in warm pee for half a week. Come to think of it, there is something pretty weird about doing anything with warm pee other than throwing it over the nearest fence.

Now you're probably wondering what on earth this has to do with rugby (beyond the fact that a bucket of steaming widdle might serve as a decent metaphor for some of Scotland's recent performances). Well the connection is found in the idea of the happy accident.

For just as the individual who first came up with the recipe for amadou probably did so when trying to do something else - though I shudder to think what - some of the most positive outcomes in rugby have really been lucky breaks as well.

Those of us who can recall Scotland's Five Nations Championship-winning side of 1999 would probably say that the performances the national team delivered that season were the best and most exciting of the past 20 years. The team was fast, slick and devastatingly effective, never more so than on that mesmerising Paris afternoon when they stuck five tries past France in the space of 20 minutes. Heroes all, but the core of the side was found in that marvellous midfield axis of Gregor Townsend at fly-half, John Leslie at inside-centre, and Alan Tait at outside-centre.

A fantastic blend of complementary talents? Well, yes, but it wasn't actually meant to happen that way. In fact, of the three, only Leslie played in the position in which he was first chosen at the start of the campaign.

For the opening match, against Wales, Townsend was picked at 13, and Tait was one of the replacements. The triumphant trio only came together when Duncan Hodge, the original starting fly-half, suffered a serious leg injury in that game. Tait came on at centre and Townsend moved to the playmaking position; the rest, as they say, is history.

It must be a devilish inconvenience to those who have made a pseudo-science of preparation and selection that there are plenty of other examples of successful sides that clicked into place despite, rather than because of, their coaches' intentions. I think, for example of the so-called 'Baby Blacks', the New Zealand side that took shape in 1986 when many regular All Blacks were serving suspensions for taking part in a rebel tour to South Africa.

Young and inexperienced, nobody gave them a prayer when they were sent out against France in Auckland that year. There were 11 debutants in their ranks, yet they scored a stunning 18-9 victory. Twelve months on, many of those players formed the core of the All Blacks side that won the inaugural Rugby World Cup in Auckland.

Sixteen years later, at the 2003 World Cup in Australia, the Wales coach Steve Hansen picked what was effectively his second-string side to take on New Zealand in their pool game, holding his star players back for an apparently more critical clash with England a few days later. Yet the fringe Wales players played out of their skins and pushed the New Zealanders all the way to the wire. The All Blacks pulled away in the last few minutes to win 53-37, but Hansen had the grace to admit he had been astonished by the performance of his team.

It happens at the individual level, too, when a player is pressed into service in an unfamiliar role and then turns in a dominant performance. A performance along the lines of the one Greig Tonks delivered last December when he was moved from full-back to fly-half for Edinburgh against Gloucester at Kingsholm. The first-choice No.10 Harry Leonard had suffered a thigh strain on the morning of the game, so Tonks was moved nearer the scrum and Jack Cuthbert was shifted from wing to full-back. Despite the lateness of the changes, both men played superbly.

Edinburgh won that game 16-10; it was their best result of the season, and Tonks and Cuthbert had made immense contributions. Quite by accident, coach Alan Solomons had stumbled upon a winning formula.

That backdrop made it all the harder to understand what Solomons was up to when he picked his side to face Ulster in Belfast last Friday and named Tonks at full-back and Cuthbert on the wing. He had the spine of a good side available and he chose not to use it. The coach tried to explain that Tonks had been injured for a long time and had to be reintegrated into the side in a less demanding position, but it sounded like the elevation of a pet theory above the blindingly obvious reality.

And, of course, it backfired, as another lame Edinburgh display resulted in them losing 30-0. They lacked shape and direction, the very qualities Tonks had added when he was moved to the playmaking role 10 months ago. That might have been a stroke of luck back then, but only a fool ignores good fortune when it comes along.