Chelsea have signed Spain defender Marc Cucurella from Brighton in a deal worth more than £60m.
Last month Brighton rejected a £30m bid from champions Manchester City for Cucurella, who handed in a transfer request after City expressed an interest.
"We did not want to lose Marc, but he wanted the opportunity of playing Champions League football with a view to accelerating his progress to Spain's World Cup squad," said Brighton manager Graham Potter.
Cucurella is the second big-money departure from Brighton this summer after midfielder Yves Bissouma joined Tottenham for £25m plus add-ons.
This summer Chelsea have brought in England forward Raheem Sterling from Manchester City for £50m, Senegal defender Kalidou Koulibaly from Napoli for £34m and midfielder Carney Chukwuemeka from Aston Villa for £20m.
They also signed 18-year-old American goalkeeper Gabriel Slonina for a reported £12m from Chicago Fire, where he will remain on loan until the end of the Major League Soccer season.
Meanwhile, 19-year-old Chelsea defender Levi Colwill has joined Brighton on a season-long loan.