Cardiff - A teak-tough defence forged by rugby league legend Shaun Edwards has helped push Wales to the brink of a Six Nations Grand Slam.
The 52-year-old Edwards, who played 36 times for Great Britain at scrumhalf or stand-off, is the most decorated player in rugby league history, with 36 winner's medals.
After hanging up his boots, Edwards switched codes, joining Wasps as assistant coach in 2001, when Warren Gatland was head coach, a position he himself took over in 2005 when the New Zealander returned home.
Edwards, the sole schoolboy player to have captained England in both rugby league and rugby union, stayed with Wasps until 2011 and during his time there, the club won two European Cups (2004, 2007) and three Premiership titles (2003, 2004, 2005).
In 2008 he became Wales' defence coach, again under the newly-named head coach Gatland and together, the pair have been crucial in helping Wales to win three Six Nations championships (2008, 2012, 2013), the first two of which were Grand Slams.
In winning the 2008 Grand Slam, Wales' tenacious defence only conceded two tries, spearheaded by chop-tackling flanker Dan Lydiate.
"Offence sells tickets, defence wins championships," was Edwards' blunt assessment at the time.
"To concede only two tries, one from an interception, one from a kick, so not one running try in five games, is massive credit for the players."
Speaking ahead of Saturday's match against Ireland, BBC pundit Jeremy Guscott added: "The most distinctive part of Wales' DNA is their defence. They have only scored nine tries so far in this tournament - the same number as Italy - but have conceded just six, the fewest of any side.
"Their fitness, durability and organisation is more of a hallmark than incredible try-scoring."
Former England centre Guscott added: "Edwards has been in charge of their defence for more than 11 years and that continuity means the defensive system is ingrained.
"Their ethos is to meet line speed with line speed. They come up flat and fast, especially close to the breakdown."
Wales' talismanic captain Alun Wyn Jones hailed his team's performance in the hard-fought 18-11 victory over Scotland that set up a chance of a Grand Slam in Cardiff on the weekend.
The Welsh produced a mind-boggling 140 tackles in the second-half of a gripping match at Murrayfield to eventually stifle a game Scottish side.
"(That was) testament to Shaun Edwards, he earned his wage this week the way we defended," Jones said.
Edwards, who was also the British and Irish Lions defence coach in 2009 on the tour of South Africa, has acknowledged his pivotal role in building up what is arguably the leading defence in the world game.
"We're pleased to get that best defence in the world title," Edwards said in January, just before Wales' opening game against France.
"Ireland are right behind us, we swapped positions from the year before, they were number one and we were two."
While Gatland's departure for pastures new after this year's Rugby World Cup in Japan has been much talked about, his coaching staff including Edwards will also be moving on.
Edwards was slated to return to rugby league to become Wigan Warriors head coach in 2020, with Adrian Lam taking temporary charge in 2019. There have been rumours, however, that he might instead return to Wasps.
"People keep saying it's my last Six Nations but I've every intention of coming back to rugby union at some stage, maybe with another country," said Edwards.
"The Wigan job is still an option but things could change, you just never know what's around the corner."
Either way, former Wales captain Martyn Williams said Edwards' departure would be "a huge loss to Wales and that's not rocket science".
"Since Gatland's been in charge Wales' defence has been legendary."