Manchester City midfielder Joey Barton has completed a £5.8m move to Newcastle after agreeing a five-year deal.
Barton's time at Man City has been dogged by controversy
Both West Ham and Newcastle submitted bids of £5.5m for the 24-year-old England international last week.
But his move to Newcastle hit a stumbling block over City's refusal to pay £300,000 that Barton was said to be owed as part of the transfer.
But the Magpies improved their offer to £5.8m on Thursday and the bid was accepted by City.
Barton said: "I am delighted to be here. As soon as it came to speaking to people
at Newcastle, it became clear they have the desire and ambition to succeed.
"The people I am going to work with have the ambitions to match mine and I hope this is the start of a successful era for myself and the club.
"I have always admired Sam from afar. The job he did at Bolton was just phenomenal."
Allardyce said he was thrilled to have landed a player he believes will be a major addition to his squad.
He said: "It's a great coup for me and this football club to get a player of such outstanding talent, something he has proven over the last four years at Manchester City."
Barton was reportedly entitled to £300,000 if he left the club without requesting a transfer, but City were reluctant to pay it as they argued he was not being forced to leave.
Newcastle manager Sam Allardyce criticised City for the hold-up and the Eastlands side responded with anger at him for making the dispute public.
The Professional Footballers' Association intervened but it seems the situation has been resolved by Newcastle increasing their bid.
Barton made his debut for Manchester City in April 2003 and has made nearly 150 appearances for the club.
He won his first England cap in the friendly against Spain at Old Trafford in February.
But his career has also been blighted by controversy and he ended the season out of favour at City after an alleged training ground assault on team-mate Ousmane Dabo.
After the Dabo incident in May, City suspended Barton, with the midfielder missing the club's last two games of the season.
Greater Manchester Police questioned Barton on suspicion of assault following Dabo's claims he was attacked during a training session at City's Carrington training ground on 1 May.
A police spokesman said Barton had been bailed until 11 July pending further inquiries.
In 2004, Barton was fined a club record six weeks' wages after stubbing out a cigar in team-mate Jamie Tandy's eye during City's Christmas party.
Barton ended up in more trouble during City's pre-season tour of Thailand in 2005, when he physically attacked a schoolboy Everton fan and had to be restrained by team-mate Richard Dunne.
Barton was subsequently sent home in disgrace and fined eight weeks' wages.