Given the fees paid for defenders in the last couple of years, the £11.5 million signing of Toby Alderweireld is surely one of Tottenham's best-ever deals.
Spurs conceded 53 goals in the 2014-15 season, but after the Belgian's arrival that figure plummeted to 35 in 2015-16 and then to just 26 last term.
Like the best centre-backs, Alderweireld is not just a fine defender in his own right; he also makes those around him better. He can certainly play a bit, too, and his move to the right side of Spurs' back three has enabled him to bring the ball forward more.