London mayor Ken Livingstone has made it clear he has no intention of curbing his tongue, despite his agreement to abide by the rules of the Labour Party.
Mr Livingstone was expelled for running as an independent in 2000
He was suspended from the party for five years for standing in the mayoral election despite failing to be selected as Labour's official candidate.
But on Tuesday the party's National Executive decided Mr Livingstone should be readmitted more than a year early.
He later said: "I've never had to curb my tongue - I am what I am."
The mayor told BBC London: "I'm delighted because the reality is we will get a better hearing for London in the government.
"I suspect this will help on a lot of projects where we have been pressing for government funding and backing and I think we will see some results of this within days, not weeks."
He had never "curbed his tongue" and nobody was asking him to do that now, he said.
Mr Livingstone argued there had been no point dragging out his expulsion.
"You basically can be out after five years on a murder rap and that does seem a little bit much for standing for an election," he added.
The decision to readmit Mr Livingstone came after he was interviewed by a five-member panel of senior Labour figures.
In what was being dubbed a "loyalty test", the mayor had to show he was ready to stick by party rules.
Home Office Minister Hazel Blears, who is on Labour's ruling National Executive Committee (NEC) conceded that there had been mixed feelings about readmitting Mr Livingstone to the party.
But she insisted the prime minister's change of heart did not amount to a U-turn.
"It's not a reverse gear on policy," she told BBC Radio 4's Today programme.
"What it's saying is that Tony Blair together with lots of other people are very concerned about what Ken would do, how it would turn out and actually our worse predictions, our nightmare scenario didn't come to pass. Ken's worked with all of us."
Nicky Gavron last month stepped aside as Labour's mayoral candidate and is now expected to run as Mr Livingstone's deputy.
Mr Blair conceded that despite his earlier fears, Mr Livingstone had done "a pretty good job" running the capital.
"My prediction that he would be a disaster has turned out to be wrong and I think when that happens in politics you should just be open about it," he told BBC London.
"If the facts change you should be big enough in politics to say your mind changes."
Mr Blair said that his comments four years ago were made without the benefit of Mr Livingstone's record.
Mr Blair added: "There will be issues upon which we have disagreements, but on the issues that concern Londoners we are in agreement and I think he is doing a good job for London."
Senior figures such as Chancellor Gordon Brown and Education Secretary Charles Clarke were thought to be unhappy about Mr Livingstone's return.
Former Labour leader Neil Kinnock had said he was "irretrievably" opposed to the idea.
'Marriage of convenience'
Liberal Democrat mayoral candidate Simon Hughes said polls suggested Mr Livingstone would have been better continuing as an independent.
The decision was a "marriage of convenience", he told BBC News 24.
Conservative Steve Norris accused Mr Blair of a cynical move to stave off humiliation in the election.
"It suits Ken, seems to suit Mr Blair but one lot of people it does not suit, I think, is Londoners," he said.
UK Independence Party candidate Frank Maloney said he would have to seriously reconsider living in the capital if Mr Livingstone wins the next election.
"This marriage between Labour and Livingstone is one made in the darker depths of hell and the only people who will suffer are the ordinary Londoners who yet again are put in second place to the personal ambition of the untrustworthy politicians," he said.
Green Party candidate Darren Johnson said: "Loyalty to London is the real test, not loyalty to Blairism."
Mr Livingstone now faces a poll of London Labour members over whether they want him as the mayoral candidate.