5) Diego Costa (Atletico Madrid to Chelsea – £32m)
There were some other names who could, arguably, have beaten the Spaniard to a place in our top five, but the striker had a big impact during his three seasons in England.
Costa scored 20 goals as the Blues won the league title in 2015, and he was just as influential when he bagged 20 more to win his second league trophy in 2017.