Former News of the World editors Rebekah Brooks and Andy Coulson had an affair for at least six years, the phone-hacking trial has heard.
Prosecutor Andrew Edis QC said he was revealing about their affair because it showed how much the couple trusted each other.
According to the BBC, jurors heard their affair, which began around 1998 until 2004, and was discovered by police through a letter saved on Brooks' computer when they searched her house in connection with the phone-hacking scandal.
The letter was written by Brooks in February 2004, when Coulson was trying to end the affair, Edis said.
It is not clear whether Coulson ever received the letter.
Edis told jurors he was not revealing the affair to deliberately intrude into the pair's privacy or to make a "moral judgment".
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The case is Britain's phone hacking scandal in which the staff from the newspaper allegedly conspired to hack the voicemail of celebrities and voice mails of murdered schoolgirl Milly Dowler in 2002 let to the shut down of the weekly tabloid in 2011.
According to the report, Brooks is facing the trial with Coulson, Prime Minister David Cameron's ex-spin doctor and former editor of Rupert Murdoch's now de-funct News of the World along with seven other employees accused of conspiracy.
However, Brooks denied charges of conspiracy to pervert the course of justice by concealing information from police investigating phone hacking and claims of corrupt payments to employees at The Sun and News of the World.
Brook's husband Charlie who was the head of security at News International will also face the trial on charges of hiding the evidence from the police.
The phone hacking scandal rocked Murdoch's media empire forcing him to shut the tabloid and embarrassed Cameron who is friends with Brooks and her husband and helped employ Coulson as key member of his team both when he was in opposition and when he came to office.
The trial continues.