London - Warren Gatland's lingering bitterness over his sacking from the Ireland job in 2001 serves as a combustible backdrop to Saturday's World Cup warm-up match against Ireland, his last home match as Welsh coach.
The 55-year-old New Zealander, who has guided Wales to three Six Nations Grand Slams during his 12-year tenure, takes on an Irish side hurting badly from the 57-15 thrashing at England's hands last Saturday.
It is fair to say that Gatland, whose treatment by the IRFU many considered shabby, and his Ireland opposite number Joe Schmidt have not seen eye to eye over the years with the latter being especially irked by his fellow Kiwi's barbed remark in 2015: "Ireland don't play a lot of rugby."
Gatland -- who made 14 changes to the side that beat England two weeks ago to go top of the world rankings for the first time in their history - did not let up ahead of Saturday's game.
"I was surprised by the Ireland result against England," said Gatland, whose ambition is guide Wales to victory in the World Cup staged in Japan from September 20-November 2.
"This is professional sport and we can put a massive dent in their confidence, and derail them a little bit."
The Wales coach - who guided the Welsh to the 2011 World Cup semi-finals - intimated that another defeat for Ireland would sow even more doubt in Schmidt's mind.
"They are under an enormous amount of pressure back home with a lot of criticism given that they haven't progressed in World Cups(beyond the quarter-finals)," said Gatland.
"They're coming here knowing they've been criticised, they'll be hurting from last week.
"There are a lot of doubts in the coaches' minds about who their best players are.
"Some of their players are getting a bit older. Is it a time to put some of the youngsters in? It's a massive game for Ireland that will answer a lot of questions."
Schmidt, who has made 11 changes to the starting line-up from the England game, has talked of a malaise in the team in the aftermath of the Twickenham nightmare.
However, the 53-year-old - who steps down like Gatland after the World Cup - said he has "seen it lift" since the heaviest defeat in his seven year reign.
Schmidt, who has steered the Irish to only their third Five/Six Nations Grand Slam in their history and two historic victories over world champions New Zealand, says he has urged the players to not change their game radically.
"The message is probably to keep your belief," he said.
"Not to go into your shell. You can't afford to go into your shell now.
"We've got two games left, we have to get out and express ourselves, we have to get out and play the game.
"I think the worst thing for us to do would be to be conservative or to take a step backwards because we're hesitant or we're not utterly confident in what we're doing or the people either side of us."
Amazingly despite the England humiliation, the Irish could still go top of the world rankings if they beat Wales by more than 15 points.
Wales's rise to world dominance has triggered controversy with outspoken World Rugby vice-president Agustin Pichot ridiculing the fact the Welsh are number one without having beaten the All Blacks.
Gatland - who is to coach Super Rugby franchise the Chiefs after the World Cup but will take a year out in August 2020 to coach the British & Irish Lions for a third time -- responded in his withering style.
"I'm quite happy to decline the position (of world number one)," he said.
"We from now will forfeit it! We didn't go in and apply for it.
"If he's not happy, then take it off us! It doesn't bother us. We officially decline the position. Thanks very much!"