Warren Gatland wouldn't be human if there wasn't some residual bitterness over the manner of his leaving Ireland. Asked on Sky Sports after Wasps' quarter-final win if his removal by the IRFU would make winning a semi-final at Lansdowne Road all the sweeter, he responded: "Absolutely."

To a degree, that was probably a bit of mischief-making. He always found it difficult to talk in clichés or play it by the book. And however much he might play it down, the cold-hearted professional coach in him will surely find it a little strange to be in the Lansdowne Road away dressing-room tomorrow after previously giving the team talk from the home dressing-room on numerous occasions.

He reminds you that a lot of water has passed under the bridge in the last two and a half years. But not enough to wash away the memories. It's been fully 15 years since Gatland first had the notion of pitching up in Galwegians after the All Blacks' tour here of 1989, and he spent most of the ensuing dozen years in Ireland.

He's something of an old-school All Black, and his hard-nosed career in the middle of the front row with the relatively unfashionable Waikato probably gave him the underdog mentality that served him well in Ireland, and especially in the west.

Fond of a beer, partial to the odd bet, he has a strong streak of loyalty to him, and it is to Galway that he still makes return treks to see friends for life. He could seem taciturn at first meeting, and though he never cultivated his public persona, two and a half years on, he is still taken aback by the warmth of the handshakes and backslaps.

That alone would dim any sense of revenge, along with his reciprocal warmth and respect for Irish rugby. "I'm coming back on Sunday with two great teams playing against each other with my head held high, saying I did a good job when I was here in Ireland and I'm doing a good job in London with Wasps."

As much as he was good for Galwegians, Connacht and Ireland, they were good for him, and such is the natural progression of these things, he is now a better coach than he was then.

No less than his achievements at Galwegians, Connacht and Ireland, Gatland's success at Wasps rather gives the lie to the agenda-driven criticisms he shipped from one detractor here in particular that he was a bad coach, or at best a lucky one.

It's also worth remembering that when Gatland took over at Wasps they were bottom of the English Premiership. They have been indisputably the best side in England for the last two years. That's a lotta luck.

"He brings a very simple approach to the game," says Lawrence Dallaglio. "He's aware of his own strengths and to be successful you have to put in place the right structures, and surround yourself with people who know what they're doing."

The Wasps and England captain credits Gatland with making a lot of tough decisions, "cutting off some deadwood and bringing in some fresh faces both playing and non-playing".

Dallaglio also extols Gatland for recognising the need for "quality rather than quantity", and the regular breaks or rest periods during the season are again a factor in Wasps motoring on toward the finishing line when others are running out of puff.

Tellingly, the playing squad hasn't changed that much - save for some astute signings in Johnny O'Connor, Rob Howley and Mark van Gisbergen. More changes were made in the back-up staff. "And then we put in the structures, without the same financial resources, as close to international as we could. In some regards I'd hope they would be better."

Aside from skill coaching, defence and video analysis, the most far-reaching change was in fitness. "We've six full-time fitness staff. Every one of our training sessions is monitored one-on-one, so there's no hiding place for the players. You can't cheat with us," he says, with a sadistic chuckle. "Apart from me leaving Ireland," he jokes, before adding: "One of the biggest losses to Irish rugby was Craig White (Wasps' fitness director, and formerly Ireland's). Talk to our guys and they say he's the best in the world."

White had left Ireland prior to Gatland's leaving. So how did Ireland lose him?

"Because somebody wasn't prepared to pay him a little bit of extra money. I think it was about 5,000 punts at the time. He was only on small money."

Like many a frustrated test coach, Gatland finds the hands-on, day-to-day beat of a club coach more enjoyable.

"The international thing is probably a little different for Team Ireland at the moment because they spend a lot of time together, but back then you might be two or three weeks together and then maybe six weeks apart, but for us we can plan for 35 weeks of the year."

The progression of players' skill and fitness levels, along with the development of the team and their game-plan, is thus more immediately and tangibly rewarding. It is also "quite a lot better" financially. That said, he's not going to deny he sometimes misses the hype of international rugby.

"When I look back on it I loved my time with Ireland, but after about five or six months at Wasps I thought to myself, 'I'm really enjoying this; I'm really happy here' with the day-to-day stuff, and a really supportive board and an incredibly supportive owner.

"It was the side things, the politics which I didn't have to deal with, some of the media stuff, the negative side of that, and dealing with committee people as well. What I found difficult in the Irish set-up was that there wasn't one person who was able to make a decision and say yes, go ahead and do that. It had to go through one committee and then be ratified by the full committee, sometimes just over small things that needed to be done.

"I loved my time in Ireland and working with the players. I'm incredibly grateful for the opportunity at 34 years of age to coach an international team. I learned a lot about myself and it played a big part in my development as a coach."

He hasn't had any contact with his erstwhile assistant Eddie O'Sullivan or any of the IRFU men who fired him, but, although contented with his lot, he retains a nagging feeling of unfinished business, to coin a phrase.

The longest pause in the conversation is when he's asked if he has any regrets about the time he spent in Ireland.

"The positives completely outweigh the negatives," he says, before adding: "I suppose if there is one regret, I would have loved to take that team through to the World Cup and finished in Ireland on my own terms, because I'd worked with the players for so long and didn't get that opportunity to fulfil something I wanted to do."

Like any coach in his position therefore, he's probably a little coloured in his assessment of how Ireland performed in the World Cup.

"They were a bit inconsistent really. They achieved their goal of making the quarter-finals, but never really fired a shot after that, but I think since then perhaps they've been a little bit more relaxed, and they had a very good Six Nations.

"They're an incredibly experienced team at the moment, a lot of players with a lot of caps who've been together for a long time. So you'd expect in the next three or four years Ireland have a serious chance of again getting Triple Crowns and are capable of at least making the semi-finals of the next World Cup."

Gatland concedes that "it took me a while" to appreciate the importance of instilling the Munster X factor into the Irish team, but that "for the last four or five years they've been the heart and soul of the Irish rugby team".

His wife, Trudi, will also come over this weekend, in a party of 28 Wasps wives, children and girlfriends, and Gatland has warned some of them what to expect.

"Probably the best supporters in world rugby. I just think they set the standard for everyone else," he says, citing their knowledge of the game, their passion, their support, their graciousness and their behaviour abroad. A lot of sporting fans could learn a lot from the Munster supporters."

He has offers pending back in New Zealand, and has long since promised Trudi that, when the time comes, a return home would be their next move. One imagines Waikato would be a starting point for the Super 12/New Zealand leg of his coaching graph.

"At some stage when I'm back in New Zealand, I think I'm going to look back and say that this was a massive part of what's helped make me as a coach. And perhaps the next time I'm in Lansdowne Road might be as part of the All Blacks. That's a dream.

"There's a lot of water to pass under the bridge before that happens, in terms of provincial and Super 12, but I think I've got the pedigree to do it."

You wouldn't bet against it.