England World Cup winner Matt Dawson says Wales defence guru Shaun Edwards is the "best coach in the world" and it was a "crime" for England to lose him.
Edwards and Gatland have renewed their coaching partnership
Dawson, who played at Wasps for Edwards and Wales coach Warren Gatland, says Wales have secured a massive coup.
"With Warren and Shaun you get defence, structure, discipline and, ultimately, you will get trophies," Dawson told the BBC's Sport Wales programme.
"I cannot emphasise enough to the Welsh public what a gem they have there."
Edwards and Gatland will renew their coaching partnership at Twickenham on Saturday when both countries begin their Six Nations campaign.
It will be their first match in charge of Wales and Edwards' first since opting to combine his Wasps job with a part-time role in Cardiff.
The RFU made a late bid to keep Edwards within the English system by offering him the job of part-time coach of the England Saxons, their Test second team.
To see Shaun Edwards go to Wales was incredible
But Dawson claims: "I was disappointed the RFU could not find a relevant opportunity for Shaun.
"In my view, and in a lot of other people's view, he is possibly the best rugby coach in the world.
"That's not something I say lightly and to see that we've let him go over the border is an absolute crime.
"To see Shaun Edwards go to Wales was incredible.
"I've been fortunate enough to play under Shaun and he is just an amazing, amazing coach.
"To join him with Warren Gatland and Rob Howley - my goodness me, if the Welsh team can't play with that coaching talent behind them then it's going to be an awful long time before they win the Championship again."
Dawson also believes Wales could emerge as Six Nations winners, three years after their Grand Slam triumph.
"My heart says England, but for some reason I can't really explain, I think it might be Wales who win the Championship."
*Watch the full feature on Sport Wales, BBC Two Wales & 2W, Thursday, 31 January (2200 GMT)