Alan Smith said the time was right to embrace a new era at St James' Park after signing a five-year deal with Newcastle today for an undisclosed fee believed to be in the region of £6million.
Smith revealed he had been close to a move to the north-east on a number of previous occasions but only now did he believe the future looked bright enough to complete the deal.
Smith said: 'I've had the opportunity to come here a few times and I just felt this time was the right time.
'I felt that with what the gaffer is doing and the new owners the club has got a lot more stability.'
The 26-year-old admitted it was a tough decision to leave Manchester United but he realised his first team chances would be limited with the imminent arrival at Old Trafford of Carlos Tevez.
Smith added: 'I decided that if you are going to stay at a club and fight your place you need the opportunity to do that.
'I felt I'd been limited. It was a big decision but I'm really looking forward to the new challenge.'
Smith's signing came as a huge boost to Magpies boss Sam Allardyce, who was also hoping to complete the signing of Brazilian Claudio Cacapa before the weekend.
Allardyce said he believed the best was still to come from Smith following his excellent recovery from the horrific broken leg which kept him out of the game for seven months in 2006.
Allardyce said: 'I think he will be a major signing for Newcastle and with his recent career-threatening injury, I think it was a life-changing experience and will make him more determined than ever.
'He is a lot more mature and he has been with the best manager in club football today seeing how you win a championship. Not only do I expect his performances to rub off on the players but also his experiences.
'This was the quickest transfer I think I have done for many many years. For Alan and his agent to have progressed it so quickly is really, very rewarding indeed, and there is nothing better than signing a top quality player.'
With Smith set to make his Magpies debut in Sunday's friendly against Sampdoria, Allardyce can now see a light at the end of the tunnel following a frustrating start to his St James' Park career.
His crippling injury list is showing signs of improving with David Rozental, Nicky Butt and Steven Taylor all training for the first time today, and Shola Amoebi and Steven Carr coming into the reckoning for the Sampdoria game.
With Damien Duff now the only certainty among Allardyce's first team squad to miss the start of the season, Allardyce said: 'It has been quite encouraging and I think there will be more coming back tomorrow.'