Aston Villa captain Fabian Delph has signed a five-year contract at Manchester City less than a week after saying he was staying at Villa Park.
England midfielder Delph's move to City had appeared over after he "set the record straight" over his future.
City agreed to meet an £8m release clause inserted into the new four-and-a-half-year contract signed in January.
"At just 25 years old, he still has his best years ahead," said City boss Manuel Pellegrini.
"He is an excellent player, I am looking forward to working with him."
Delph completed a medical on Friday and will fly to Australia over the weekend to join his new team-mates for pre-season training.
He will wear the number 18 shirt which Frank Lampard, now at New York City, wore last season.
Aston Villa released a 30-word statement confirming their captain's exit.
"Aston Villa can confirm that Fabian Delph has exercised the release clause in his contract and will join Manchester City," it said.
"We'd like to wish him success in his future career."
Delph released a statement last week after reports of his original medical at City, saying: "I'm not leaving, I'm staying at the football club."
On Friday, he said he had spoken to his England team-mate and City goalkeeper Joe Hart - as well as Villa's new signing from City Micah Richards - before signing.
"Micah Richards told me that as far as he is concerned, this is the best club in the world and he had the time of his life here," added Delph.
Former Leeds player Delph did not travel with the Villa squad for their pre-season training camp in Portugal.
He helped Villa retain their Premier League status last season, making 28 league appearances, and also played a key role in their run to the FA Cup final, where they lost 4-0 to Arsenal.
He made his England debut against Norway last September and has six caps.
Find all the latest football transfers on our dedicated page.