The memo on the talks, on Iraq strategy, was sent to MI6
A leaked record of an Oval Office meeting between Tony Blair and George Bush contained key intelligence details about Iraq, the Old Bailey has heard.
Matthew Rycroft, now ambassador to Bosnia, said it was only supposed to be circulated to those "dealing directly with British policy in Iraq".
David Keogh, 50, and Leo O'Connor, 44, are accused of leaking the memo.
The men, both from Northampton, deny three charges under the Official Secrets Act 1989.
The court was earlier told civil servant Mr Keogh gave the memo to political researcher Mr O'Connor at a dining club in Northampton.
It was passed to Northampton South MP Anthony Clarke, who called the police.
Contents of the memo are so sensitive that much of the trial is being held behind closed doors.
It records details of a two-hour White House meeting between Mr Bush and Mr Blair in April 2004, the Old Bailey heard.
The discussions took place during a two-day visit to the United States by Mr Blair.
Notes were taken by Mr Rycroft, Mr Blair's private secretary on foreign affairs, and he prepared a series of memos focusing on the different areas they covered, including Iraq.
He designated the letter as "personal" and "secret", adding a comment at the top of the memo that it was "extremely sensitive" and should only be seen by those "with a really need to know".
Copied to MI6
Asked on Friday in court why this comment was added, Mr Rycroft said: "To make the same point but even more so and to make it absolutely clear to each of the people that I was sending the letter to the sensitivity of this particular discussion and the subject matter that the Prime Minister discussed with President Bush.
"Parts of it had a direct bearing on the British military presence in Iraq and the overall policy context of Iraq."
Asked why the memo was also copied to MI6, he paused for a moment, before saying: "It was relevant to their function in and about Iraq."
John Farmer, for Mr O'Connor, questioned Mr Rycroft about why given its sensitivity, the document was circulated to Mr Blair's director of communications David Hill and his official spokesman, Tom Kelly.
They were among 33 recipients of the memo and 87 who eventually saw it, the court was told.
Mr Farmer asked: "Was it in your contemplation in April 2004 for any part of this document to be made public?"
"Absolutely not," Mr Rycroft replied.
Mr Rycroft said he did not believe that the Prime Minister intended the document to be made public.
When asked why Mr Hill and Mr Kelly were provided with a copy of the document, Mr Rycroft replied that it would give them a more complete knowledge of the Prime Minister's policies.
The trial was adjourned until Monday.