Shaun joined English Premiership team Wasps in the summer of 2001 as Assistant Coach. He was promoted to Head Coach in 2005.
Wasps went on an unprecedented run of success becoming English Champions for three consecutive years 2003, 2004, 2005- also in 2004 Wasps won the European Championship for the first time in their history.
In the three English finals, Wasps only conceded 1 try in all three games.
Sir Ian McGeechan took over the Director of Rugby role in the 2005/2006 season and the success continued. Wasps won the Anglo-Welsh Cup in 2006, The European Championship in 2007 and were once again crowned English Champions in 2008.
In 2008 Shaun teamed up again with Warren Gatland on the International front with Wales. Success was immediate winning the 6 Nations Title with a record of only 2 tries conceded in the whole competition on the way to a Grand Slam.
Another Defensive record fell with Wales not conceding a try for 400 minutes in the 2013 campaign.2009 saw Shaun selected as Defence Coach for The British and Irish Lions, a campaign very narrowly lost in controversial circumstances against The South African Springboks, the No1 World ranked team.
The World Cup of 2011 saw Wales make the semi final, overachieving expectations averaging only 10 point a game being conceded.
Also in 2011 Shaun left Wasps to concentrate fully on International Rugby. Wales went on to win the next two Six Nations in 2012 with another Grand Slam win in 2013. Another Defensive record fell with Wales not conceding a try for 400 minutes in the 2013 campaign.
Wales qualified through the group of death in 2015 rugby World Cup with the best defensive record in the competition. Shaun was part of the Welsh team that went 17 games undefeated in 2018-2019 (Welsh record).
2019 World Cup Wales lost in the semi finals to the eventual winners South Africa.
In December 2019 after 12 years with Wales Shaun joined French National team on a four and a half year contract in the build up to the 2023 Rugby World Cup in France.