Jurors in the hacking trial were told to decide the truth of the affair between News of the World editors Rebekah Brooks and Andy Coulson to establish if they shared their hacking secrets.
The timescale of the relationship was important in considering if they both knew about the hacking of schoolgirl Milly Dowler's phone and the voicemail from home secretary David Blunkett to Spectator publisher Kimberly Quinn, the Old Bailey trial heard.
Resuming his closing speech, prosecutor Andrew Edis QC turned to the letter of February 2004 in which Brooks declared she had been waiting six years for Coulson, saying she confided in him.
Mr Edis said the letter which was never sent was "at odds" with what both defendants had said in their evidence.
He told the jury: "Mr Coulson told you soon after this letter in 2004 they got back together again and it carried on until he left the paper in January 2007 which is not at all what Mrs Brooks told you, so you have to decide.
"Why does it matter? It matters for two reasons. One - at the time of the Milly Dowler hacking were they in the sort of relationship that would involve them sharing work-related confidences with each other without inhibition?
"Secondly, were they back together again by August 2004 so that the same thing applies. Why does that matter? That is the Blunkett hacking.
"It is not the case to make you think any worse of either of them. That is not the point. It is a factual relevance. Were they at daggers drawn...or were they in fact very close."
Mr Edis was outlining the evidence against Coulson, Brooks and former managing editor Stuart Kuttner on the first charge they face of phone hacking.
He said private detective Glenn Mulcaire's initial contract in September 2001 for £92,000 a year must have been authorised by the editor at the time - Brooks.
He said: "It was not necessarily her idea but she must have said yes. That act of awarding Mr Mulcaire his contract in the first place is we suggest strong evidence against Mrs Brooks on count one."
He also told the jury that they should consider the separate charges Coulson and Brooks face of conspiring to commit misconduct in public office in relation to the hacking charge.
If Goodman and Coulson are guilty of conspiring to pay police officers for royal directories, it showed they were "acquiring the raw material for phone hacking", Mr Edis said.
And while conspiring to commit misconduct in public office was different from phone hacking, in Brooks's case, if guilty of the one charge, it would also demonstrate a willingness to "allow your journalists to commit crimes in order to get stories", the prosecutor asserted.
All seven defendants in the trial deny the charges against them.
Mr Edis said that Brooks's letter was not "rambling and incoherent" but was in fact "carefully written and eloquent".
The lawyer went on to outline why the interception of murdered schoolgirl Milly Dowler's voicemails in spring 2002 was key to the case against Brooks, Coulson and Kuttner for allegedly conspiring to hack phones.
After Milly's phone was hacked by Glenn Mulcaire, journalists were sent to Telford in search of her before Kuttner told police about the voicemails which suggested she might be alive, the court heard.
A story was run in the first edition of the paper, which was then changed in the final edition on April 14, 2002.
Mr Edis told jurors: "The Milly Dowler event is extremely important to this case because each of them - Mrs Brooks we say, she denies it, but Mr Coulson and Mr Kuttner and they do not deny it - were all directly involved in this.
"From that moment on if not before, from April 2002, the three defendants charged on this indictment all knew about phone hacking and what is common ground is none of them lifted a finger to stop it and Mr Mulcaire continues to get his £1,700 odd a week afterwards as he had before.
"No-one got sacked and the police were not called despite everyone knowing.
"The only inference is the people who found out about it at this stage were perfectly happy that it should carry on."
Mr Edis went on to describe Coulson's account of the David Blunkett hacking episode in the summer of 2004 as "preposterous".
Coulson said he was shocked and initially told Neville Thurlbeck to stop when the reporter told him about the voicemail of Mr Blunkett declaring his love for Ms Quinn.
But he was persuaded it was in the public interest, although those aspects were not in the resulting story, Mr Edis said.
The prosecutor said the jury should reject Coulson's account, saying: "He knew what had gone on and he was perfectly content.
"After all, Mr Mulcaire carried on getting his money and as we know carried on hacking so that by 2005, early 2006, the amount of hacking that could be proved was absolutely phenomenal. He of course says he assumed it was Neville who had done it himself. Why didn't you ask?
"His account of his behaviour in relation to this story is preposterous."
The lawyer asserted there had been an arrangement between Coulson and Brooks that she would publish Ms Quinn's name in the Sun the day after the NotW broke the story.