The police and Crown Prosecution Service say the conviction of cleric Abu Hamza al-Masri was the outcome of a "close and painstaking" joint effort.
Previous evidence against Abu Hamza was judged 'insufficient'
The statement came after the police criticised a lack of action by the CPS, prompting the CPS to defend its own decisions not to prosecute earlier.
Abu Hamza, 47, was jailed on Tuesday for inciting murder and racial hatred.
Police said they had given evidence three times to the CPS before enough was presented for a prosecution.
Abu Hamza, from London, was jailed for seven years after an Old Bailey jury found him guilty of 11 charges, including soliciting murder and inciting racial hatred. He was cleared of four charges.
The joint statement came from the head of counter-terrorism division of the CPS, Sue Hemming, and the head of Anti-Terrorist Branch Metropolitan Police, Peter Clarke.
ABU HAMZA VERDICTS
Guilty of 6 charges of soliciting to murder
Guilty of 3 charges related to "stirring up racial hatred"
Guilty of 1 charge of owning recordings related to "stirring up racial hatred"
Guilty of 1 charge of possessing "terrorist encyclopaedia"
Not guilty of 3 charges of soliciting to murder
Not guilty of 1 charge related to "stirring up racial hatred"
It said the police made three submissions to the CPS - two in relation to potential offences committed in Yemen and a website, and the third relating to the trial.
Senior prosecutors who reviewed the submissions concluded in two cases "there was clearly insufficient evidence for a prosecution", the statement said.
The decision to prosecute was taken by the CPS in October 2004.
The police had earlier criticised CPS, by saying it had sent it information "on several occasions" since 1999 but no action was taken.
The CPS defended its actions, saying there was "insufficient evidence" to act sooner.
A CPS spokesman said evidence presented before the end of 2003 - relating to different investigations to the Old Bailey race hate trial - was found to be "insufficient to prosecute".
"The first tape in relation to this matter [the Old Bailey trial] came to us at the end of 2003 and the majority of tapes submitted for the prosecution came after the searches in May 2004 when they were seized."
Meanwhile, Abu Hamza's lawyer has given BBC News access to papers relating to some of the MI5 and Special Branch interviews with the cleric in the late 90s.
The papers show the extent of the contacts the authorities had. His lawyer says that is why he thought he was doing nothing illegal.
BBC Home Affairs Correspondent Margaret Gilmore said: "If you look at those transcripts, you will see what a close relationship Abu Hamza had with MI5.
"Whether they admit it or not, you could be forgiven for getting the impression there was an unspoken understanding that as long as they kept tabs on him, he was allowed to be able to do as he pleased.
"Now, 9/11 changed all that - Abu Hamza overstepped the mark and police stepped in - and they eventually changed their policy on all that."
The Times has reported that the cleric had links to those responsible for the 7 July bomb attacks.
But BBC Security Correspondent Frank Gardner said Whitehall officials did not have any intelligence to suggest that any connection existed.
Hamza could still face extradition to the US on terrorism charges when he is released from jail in Britain.
He will remain at Belmarsh high security prison, where he has been held since his arrest in 2004. It is understood he will be eligible for parole in 2008.
Shadow home secretary David Davies said a judge should investigate "why it took so long to bring this prosecution".
"It would appear the only reason Abu Hamza was actually prosecuted was because the US was seeking his extradition," he said.