We stay in Dunedin Saturday night and while breakfast for the group is slated for 7.30am Sunday, there’s two of us who’ll be up a bit earlier. Jon Gardner is the Crusaders’ Head Performance analyst, and we’ve booked a 4am room service breakfast. One small detail: Jon’s as proud a Welsh man as you’ll find, a really good guy who is unbelievably psyched at the prospect of a Welsh Grand Slam.

It’s one of the vagaries of living down here that getting up in the dead hours becomes the norm. Jess was slagging me that I might even try to unearth coverage of the Pres-Christians Cup final in the early hours of next Monday. At least I think she was slagging. Am I that bad?

Yes you are, she said.

You end up doing round-the-clocks. The night we beat the Hurricanes at the end of last month, I came home, watched the tape back then went straight into France-Scotland, and afterwards Wales-England before crawling into bed around 8 am Sunday morning.

Gardner used to be with the Gwent Dragons and reminds me all the time ‘I’ve done alright haven’t I?’. The video analyst who properly understands the game is particularly helpful to a coach because he or she is that extra pair of coaching eyes who can either validate what you are thinking or offer a thought-provoking alternative. Jon’s one of those.

We agree on one angle though: It’s crazy how much of an upside there is from one 80 minutes of rugby for both Wales and Ireland in Cardiff tomorrow.

The swing in the Irish psyche is well practised and will go from one end of the spectrum to the other again if Ireland win tomorrow – from doom and gloom after the England game to potential World Cup winners by Monday morning.

It’s hard to downplay the significance of this one though. This game is Ireland’s Six Nations in 80 minutes. Try to gauge where Ireland are at after the first four rounds of the tournament. You will quickly realise it’s impossible because any proper analysis has to wait for the last game in Cardiff. This is D Day. The train was derailed in Round 1, was just about chugging along in Rds 2 and 3 but is humming again after France. Now they can travel full circle in 80 minutes. Wales in Cardiff is a challenge that’s brimful of searching question. Joe Schmidt and the players full expect to get tested in every aspect of their game. It’s the optimum environment for rugby, probably the best stadium in the world for such an occasion.

Irish fans will quarry their fair share of tickets but this is a Welsh occasion, and it’s not like Warren Gatland’s looking for a Six Nations-ending high — this is Wales at their hungriest, on the point of achieving something massive in a fourth Six Nations Grand Slam.

It’s amazing in many respects that it’s the middle game of the three on the final Six Nations weekend, but as we’ve seen in stark terms recently, money talks and everything else takes a ticket and stands in line. I took a quick double-take this week to make sure that England-Scotland was scheduled as the climax to the weekend. Odd to say the least.

Joe has a good idea of his World Cup shape and strategy at this stage but he will still be on the look-out for big and little moments from a cracking game in a daunting environment like Cardiff. A victory gives Ireland such a platform for positive planning and atmosphere going into the autumn.

The flipside is that a defeat tomorrow generates a feeling of under-achievement as players leave international camp. You don’t want that. The Ireland of gallant failure and positives in defeat is of a different era now. We are the No 2 ranked side in the world, with 20 wins out of the last 22. It’s a gut thing when you look at Healy, Best, Furlong, that entire back row of O’Mahony, O’Brien, Stander, the leaders behind it, and you feel this is not an Ireland that takes solace in defeats, however slim. We have had our wobble, and if Ireland is a top, top side, normal service resumes at 2.45pm tomorrow. Losing to Wales is never a good day out in the office, even if it this is a 50-50 game for the visitors.

I like Gareth Anscombe at 10 for Wales, despite the noises for Dan Biggar. Gatland has a lovely cocktail there of his starter managing the team well and Biggar coming in as the closer. Whether it’s a combination to take down this well-balanced Ireland XV is questionable.

It’s unrealistic not to factor in the venue. Home advantage is like an in-built extra in rugby, more so in Six Nations rugby with all that history swirling around and those voices that whisper to you from your first test that home games must be won. It’s an unwritten rule.

For all my years playing, you just felt you had to find a way to win at home. The psyche hasn’t changed that much and the stats underline that it’s still damn hard to win away games in this tournament.

Hence, what a double-deflater it would be for Wales to lose to Ireland and to lose a Grand Slam. That’s the point of what Jon Gardner and I have been saying — it’s a moment of opportunity for Welsh rugby but there’s so much on the line for them, and so much to gain too for Ireland if they finish this Six Nations by winning in Cardiff.

We discussed the importance of proper leadership here last week in the context of Rory Best, and both himself and Johnny Sexton stepped up against France as true generals do. But in his own assured way, Conor Murray was busy finding his own groove with that brilliant, unfussy temperament of his.

There’s a reason we called him Federer. He has that kind of vibe going on. The same as Dan Carter.

Compare that ability to find poise in a maelstrom to the number of opportunities Scotland fluffed against Wales and you get a clearer understanding of what constitutes precision at test level. And what does not? Wales’ defence was really strong but it’s been another hugely underwhelming Six Nations for Gregor Townsend, He will reflect on that Ireland game with regrets too.

Welsh resilience is a constant under Gatland but one cannot ignore either the fact they were down 16-0 to a bang average and out-of-sync France side on the opening weekend. Comparing that French side to the one so meek in Dublin last Sunday is a stretch, I accept, but it’s not without relevance either.

Therefore, you can take it as read that Joe will have pinpointed two key areas of weakness where he goes after Wales — if he makes progress in those moments and gets two tries in the process, Ireland will win.

It’s ten years since Rory Best was a Grand Slam winner in Cardiff. What a nice final venture it will prove if he can bring that experience to bear and have another big day beating Wales.

Let’s call it out, sportspeople enjoy trophies, but there’s a gorgeous feeling of perverse satisfaction too when you can mess up somebody else going for a Grand Slam.

We fly back from Dunedin to Christchurch on Sunday.

It’s a short hop but if I could I’d willingly hunker down for another 24-hour flight and transport myself back to Aghada in East Cork for Monday’s walk in support of Kieran O’Connor, the Cork footballer who has put all our insignificant moans into perspective these past few months.

Christchurch might be 13,000 miles away from Cork but that hasn’t diluted my pride at the support Kieran’s situation is getting across the social and sporting divide at home. It’s inspiring.

Whether Ireland win or lose tomorrow, don’t look for a reason not to be walking with your jersey on in Aghada come Monday at 2pm.