So. What the hell happened? Let’s have a look.

Leinster v Northampton. The Aviva stadium clock was ticking down fast, just a minute or so was left in the Champions Cup semi-final. Then, out of the blue, Leinster went wide, and suddenly Josh van der Flier was charging towards the line, for the winning score, or so we all thought.

What followed left French referee Pierre Brousset with one of the trickiest decisions he’ll ever have faced. The more it was replayed, the more complex it seemed to become. There were a lot of ingredients in this particular dish.

First, let’s clear a couple of things up. If the ball hits the corner flag/post it is not out of play − it used to be aeons ago, but not anymore. Secondly, Ross Byrne’s ‘touch down’ could not be considered as he was off his feet. And lastly, while penalty tries are normally accompanied by a yellow card, not all yellows are penalty tries.

Van der Flier was bowled over short of the line, it was within reaching distance. Brousset penalised and carded Northampton’s Alex Coles for not releasing the Leinster man, so he must have deemed Coles as a tackler, which is one thing he certainly was not. But, crucially, he did not award a penalty try. I believe that he should have, here’s my reasoning.

The players wait patiently as Pierre Brousset considers his vital late decision. Photograph: David Rogers/Getty Images

What mattered here occurred when Coles went to ground onto van der Flier. That is specifically and sensibly covered in the law bible. It outlaws an opponent from falling on a ball carrier who is on the ground. It is expressly forbidden. Otherwise, van der Flier could very probably have reached out and scored. Probability is the key factor for awarding a penalty try, and that would have been the correct call. If Brousset had started at the beginning as he considered the events, who knows, he might well have come up with the right answer.

While many are boiling the result down to this one decision, Northampton could question, if they were bothered, the validity of a first-half try by the ubiquitous van der Flier. Max Deegan was tackled, but remained in possession. A tackled player must immediately place the ball on the ground, or pass it, no delay. However, it looked as if Deegan did delay his pass to van der Flier with a feinting movement, which prevented Northampton contesting possession. Not nearly on the same scale as the van der Flier incident, but the score could have been ruled out.

Leinster's Josh van der Flier scores a try that could easily have been ruled out by the officials. Photograph: Laszlo Geczo/Inpho

“But the best team won,” is often how the argument goes, which it did, but that argument doesn’t stand up in the professional game, so Brousset stands accountable. There were reasons which contributed to Leinster’s loss, and these have been well documented in this paper by Gerry Thornley. Overall, Leinster played second fiddle in just about every section of the orchestra, with the pack being far too late to tune in. The key battle at half-back was all too easily won by the excellent Northampton duo of Alex Mitchell and Fin Smith − they didn’t miss a beat.

The much-lauded Jacques Nienaber defence was holed frequently below the waterline, and the Leinster ship was listing badly as the clock ominously ticked down. Leaking five tries was a disaster for what we’ve been persuaded to believe is a near infallible defensive system. Clearly, it is not.

No doubt social media will give Brousset a horrible time of it. In all matches there are queries around some scrum and breakdown calls, but overall he was fair and equitable. But the referee will be remembered, and judged, on just one moment, a moment which could not have had greater importance. Some will argue that it shouldn’t have come down to just one incident, but the problem is that it did. It definitely did.

Ireland's Andrew Brace gave a fine performance in the Champions Cup semi-final betweem Stade Toulousain and Bordeaux-Begles. Photograph: Lionel Hahn/Getty Images

A very sunny Bordeaux saw a wonderful match with the home team stealing an unexpected march on Toulouse, so both favourites have gone. The scoreline of 35-18 did not reflect the effort of the champions to keep their grip on the trophy. Ireland’s Andrew Brace was in charge, and had a good day out.

He was much more assured in his communication, and there was less of it too. Of course, I can question a few forward pass calls, one particularly bad one, which probably came from his assistant. And did he get all the breakdown decisions right? No, indeed he didn’t, but we all know that’s an impossibility. So, in the land of the vine, I hope that a relaxed Brace enjoyed an evening glass or two of Bordeaux’s finest.

The semi-final results mean that the old guard has gone for this year, the destination of the Champions Cup will now be between Northampton and Bordeaux. The former won the cup 25 years ago, pipping Munster by a solitary point, then lost to the famous Leinster comeback in 2011. The French team have never got close to this stage. Both semi-final winners took the spoils by scoring five tries each and playing a fast, expansive game − we hope to see more of that in Cardiff.

The final pairings of both cups dictate that English and French referees can’t be considered, cutting down the appointment options for EPCR referee manager Tony Spreadbury. It underlines the unacceptable situation where Wales, Scotland and South Africa have nobody capable of refereeing at this level. There are only three referees in the frame. The Georgian Nika Amashukeli, Ireland’s Andy Brace, and Andrea Piardi of Italy.

So, although the conclusion to this year’s tournament is a mouth-watering prospect, it will have a different taste. It’s a crying shame, but Leinster won’t be there.