In his first season at West Brom, they finished 8th, their highest finish since 1981. He set club records for highest number of wins (14) and points (48) in a Premier League season.
During that season, they won 4 consecutive league matches in a row for the first time since 1980. He was named Premier League manager of the month in November 2012.
He was effectively sacked by West Brom the following season in December whilst sitting 16th in the table. Look where they are now!
He took the Reading job half way through a season, saved them from relegation and got them to their first FA Cup Semi Final in 88 years, only losing 2-1 to Arsenal after extra time. He was sacked half way through the following season after talking to Fulham about taking over at Craven Cottage.
So he only ever had one full season as a manager in England and his record in that season was exceptional. In his 3 other half seasons, he managed a 16th placing in the Premiership, saved a club from relegation and got them to an FA Cup Semi Final.
Allied to his record at Kilmarnock and his assistant manager experience at Newcastle, Chelsea, West Ham and Liverpool, he is by far the best candidate.
And while I'm at it, I always thought it a disgrace that Clarke won only 6 caps for Scotland while Tom Boyd won 72. They were both at Chelsea at the same time for a short period and whereas Clarke established himself as a regular and played over 300 games, Boyd was papped out after 6 months in a swap deal for Tony Cascarino!