Michael Essien has finally completed a £24.4m move from French club Lyon to Premiership champions Chelsea.
Midfielder Essien, 22, has signed a five-year deal and becomes the Stamford Bridge club's record signing.
"I wanted him because I was looking for a player to finish what is a very strong squad in every position," said Chelsea boss Jose Mourinho.
"We believe he is the best we can get for his position and he can play anywhere in midfield."
He added: "He's young, has a lot of ambition and he has the profile of the player we want.
"I know the questions will be around the amount of money Chelsea had to spend to bring him here but that is the reality of modern football.
"Big teams only want big players, big players are in big clubs, big clubs want to keep their big players.
"The player is here and we think we have a really strong squad with a lot of space for improvement because everyone is very young."
2000: Joins French first division Bastia from Ghana's Liberty Professionals
2003: Joins French champions Olympique Lyon for £5.3m
2004 & 2005: Helps Lyon to consecutive French league titles
Aug 2005: Joins Chelsea for £24.4m
Essien has secured a work permit and Chelsea are awaiting international clearance for him to play against Arsenal in the Premiership on Sunday.
Chelsea have pursued Essien all summer, and had bids of £10m, £16.75m, £18m, £21m and £21m plus Tiago turned down.
But the midfielder will now become the Blues' record signing, exceeding the £24m they paid Marseille for Ivory Coast striker Didier Drogba last summer.
Essien said: "I wanted to come to the Premiership and now I am very happy.
"I am in love with the Premiership. I am pleased to be with Chelsea.
"It is going to be tough but I am ready to fight for a place in the team.
"I don't think it will be a problem to adapt because I speak the langauge and I have some friends in the team.
"Physically I'm okay because I trained normally with my former club."