Denis Healey kept in the dark about Polaris upgrade
At the height of the Cold War, crucial information about Britain's nuclear deterrent was concealed by civil servants to ensure their plans for an upgrade were approved.
It might all have been an episode of the satirical Yes Minister series.
In the mid-1970s, senior civil servants come to the conclusion that Britain should continue with plans to upgrade its nuclear weapons system, Polaris.
However, sensing that then Chancellor of the Exchequer Denis Healey might not be convinced by their reasoning, they decide to keep vital facts from him.
In the end, the cheques are signed, the scheme goes ahead and "Sir Humphrey" gets his way. But this was real life and not a TV sitcom.
The 'Moscow criterion'
Throughout the 1960s and 70s, the Cold War continued to dominate relations between East and West.
Both joined talks aimed at curbing the arms race in the knowledge that it was something neither side could afford to lose.
But when news came in that the Soviets were developing an anti-ballistic defence shield around Moscow, many in Whitehall and the military began calling for Britain's Polaris nuclear system to be upgraded.
They argued that Britain would no longer have a credible nuclear deterrent if it could not target the Russian capital - a theory which became known as the "Moscow criterion".
The proposed solution was to upgrade Polaris in a project called Chevaline which, it was hoped, would be able to penetrate the planned defence shield around Moscow.
However, a secret minute, number 1141/5, made clear that, although the existing system could not target the Russian capital, it could strike at least 10 other large Soviet cities.
Some senior civil servants feared that, if Chancellor Healey knew this, he might decide that it was not worth upgrading Polaris after all.
No 'need to know'
So they recommended that the secret minute (put into the public domain briefly in 2005 and now reclassified) was kept from him on security grounds.
On 27 November 1975, a senior defence official wrote: "The permanent secretary to the secretary of state would write in parallel to the permanent secretary to the prime minister to explain that the secretary of state's minute had not been copied to the chancellor of the Exchequer because the latter did not 'need to know' the situation."
The projected cost of the Chevaline scheme was originally put at £30m, though it would eventually cost £1bn.
At the time this was a large sum of money, particularly given that Britain's economy was then on its knees. Cancelling it would save the chancellor a large sum of money - another factor, it was feared, that might persuade him to cancel the project.
Secret minute 1141/5 reveals that Cabinet Secretary Sir John Hunt said: "Such savings might be very attractive to the chancellor."
A later document suggests further sleight of hand.
Dated 7 June 1976, a Ministry of Defence official talks of concealing the costs of the programme, stating that if questions arose: "It should not prove difficult to concoct a story."
So, all these years later, how does the former chancellor feel about being kept in the dark about elements of a scheme that he signed the cheques for?
Lord Healey, now 93, is in no doubt why he thinks it was done: "They didn't want to tell me because they knew I understood the issue perfectly well and would cancel.
"And that's one of the worries I think ministers must have about civil servants, that they will withhold information which they think will lead to a decision they don't like."
Lord Healey believes it was "disgraceful" that this was done, even if it was on the grounds of national security.
I asked him how he felt about the implication that even he, chancellor of the Exchequer and former defence secretary, could not be trusted: "Not be trusted to agree with them. Well, sod them!" he replied.
Given the deep divisions on the nuclear issue within Harold Wilson's minority government, I asked Lord Healey whether if he had known all the facts and chosen to oppose Chevaline what might have happened?
"I think I could have got a majority (in cabinet), even if Wilson had opposed me," he said.
Could a row over an issue as big as this perhaps have brought the government down?
"Conceivably, I think so, yes."
Most of the civil servants named in these documents have since died but one, who declined to be interviewed, said it was all just "office politics".
David Owen, now Lord Owen, who was foreign secretary between 1977 and 79, disagrees strongly.
"No, it's quite a disgraceful judgement because he (Healey) did have a need to know. I think Sir John Hunt (former cabinet secretary) crossed the line and he should not have been party to the decision to freeze Denis Healey out," he said.
"That was, I think, a reprehensible decision, and it should be made clear to future cabinet secretaries where the line is. And he crossed the line."
It seems clear that those officials involved in keeping information from the chancellor, most of whom had distinguished careers serving their country both in peace and war, were acting in what they genuinely believed to be the national interest.
But, in a democracy, can actions of this kind by civil servants ever be justified?
Lord Healey thinks not: "If civil servants conceal the most important facts about the decisions you have to take, they're betraying their country. It's a form of treason."