David Keogh and Leo O'Connor stand trial at the Old Bailey
An MP's researcher who was passed a secret Downing Street document by a senior civil servant had never been "so worried and so fearful", a court heard.
Leo O'Connor was given the memo of an Oval Office meeting in April 2004 between Tony Blair and George Bush by civil servant David Keogh.
Mr O'Connor, 44, and Mr Keogh, 50, who are both from Northampton, are on trial at the Old Bailey.
They deny making damaging disclosures under the Official Secrets Act.
Mr O'Connor, who worked for anti-war Labour MP Anthony Clarke, said he was approached by Mr Keogh and told about "some quite embarrassing, outlandish statements" in the four-page document.
But he told the jury that he took the claims, which are so sensitive that much of the trial is being heard behind closed doors, with a "pinch of salt".
"I wasn't convinced that this thing actually existed," said Mr O'Connor.
"My recollection of the conversation was around, 'can you get this to the people that can do something with it?' I think at the time I said yes.
"If it was true, and at the time I wasn't convinced it was true, then this needed to get back to where it actually belonged."
The pair arranged for Mr Keogh, a Cabinet Office communications officer, to bring it to Mr Clarke's constituency office, where Mr O'Connor worked, and make a copy.
Given to MP
"I can't remember a time in my life when I have been so worried and so fearful," Mr O'Connor said.
"It was the fear of knowing that I'd got something that I shouldn't have been in possession of, that I needed to get back to where it came from."
Asked if he intended to send copies of the document to newspapers or members of Parliament he said: "The thought never crossed my mind."
Instead he decided to put it in the papers of his boss Mr Clarke, so that he could give it back to Downing Street and an investigation could take place, he told the jury.
He told the Old Bailey he had been "100% confident" Mr Clarke would return it to the appropriate people.
The court heard how he spent more than 10 years in the Territorial Army before resigning after being convicted of assaulting a fellow TA soldier.