Manchester United have confirmed the signing of midfielder Ander Herrera from Athletic Bilbao.
The La Liga club rejected a £29m bid from United for the Spaniard, 24, on Thursday morning.
But Herrera has now activated a clause in his contract that has allowed the first transfer of Louis van Gaal's tenure as manager to proceed.
"Signing for Manchester United is a dream come true," said Herrera, who has agreed a four-year deal.
"I have joined United to do all I can to help the team reach the club's objectives.
"Having arrived on Tuesday, I'm excited to now be living in Manchester and I can't wait for my first game in United's famous red shirt."
United attempted to sign Herrera last year, only for the deal to fall through in farcical circumstances.
The Premier League club have moved much more quickly this time around to capture a player who impressed against them in the Europa League in 2012.
Athletic said earlier on Thursday that they had rejected bid from United, even though it matched the figure stated in Herrera's release clause.
Old Trafford officials viewed it as a political stance from Bilbao, aimed merely at appeasing their own supporters.
"We aspire to have players whose first choice is to defend our shirt," said the Basque outfit in a statement on their own website. "Ander's decision doesn't match that, which is disappointing.
"It's not a pleasant moment, but it doesn't alter our philosophy nor our way of working."
Bilbao-born Herrera remains thankful to his home-town club.
"I will never forget my time with Athletic Club," he said. "I'd like to thank the fans and staff for all their support and above all wish all my fantastic former team-mates all the best for the future."
Herrera will report for pre-season training next month. It is anticipated he will be part of United's tour party when they head to the United States on 18 July.
"Ander is a fantastic young player, with great energy and creativity," said United assistant manager Ryan Giggs of the midfielder, who is yet to be given a squad number.
"We believe him to be one of the brightest young prospects in Spain and I am certain he will be a big hit with the United fans."
Though he is on World Cup duty with the Netherlands, Van Gaal has already had an impact, sanctioning contract extensions for winger Antonio Valencia and defender Patrice Evra.
As yet, though, there has been no fresh bid for Southampton left-back Luke Shaw, who was the subject of an offer from United prior to England's World Cup campaign.