Henri Lansbury has joined Nottingham Forest from Arsenal on a permanent deal for an undisclosed fee after signing a four-year contract.
Sky Sports earlier on Tuesday revealed the 21-year-old had passed a medical with the Championship club ahead of his switch to the City Ground.
And the England Under 21 midfielder has now completed his Arsenal exit after just eight senior appearances for the club.
Lansbury has previous experience in the Championship having last season spent time on loan at West Ham United, who he helped to promotion to the Premier League.
He achieved the same feat while on loan at Norwich City in 2010/11 and is now hoping to make it a third promotion to the top flight with Forest.
Lansbury told his new club's official website: "I'll do everything in my power to make it a hat-trick with Forest. I'm not sure whether or not I am a lucky charm but I'll be out to do all I can to get Forest up this season.
"Having been at Norwich and West Ham when they were promoted I suppose I've seen at first-hand what is required and I'm in no doubt that Forest have what it takes to go up.
"There are a lot of good players here and I just can't wait to get working with them in training on Thursday.
"I know I am leaving a huge club in Arsenal, where I have been since I was eight but the time is right for me to move on and I'm delighted to be joining a club of Forest's stature in the game.
"The stadium is great and everything about the club feels right. I'm also aware of the manager's reputation for wanting to play the game in the right manner. He's renowned for encouraging a passing game - and that suits me fine.
"It's been a bit hectic this week since the possibility of a move was mentioned and all I want to do now is get playing for the club and settle in as soon as I can."
A statement from Lansbury's former club read: "Everyone at Arsenal would like to take this opportunity to thank Henri for his contribution to the club and wish him well in his future career."