Two stories in the past week have given me a sharp memory jolt, reminding me – not that I needed reminding - that the past is always with us.

The first was the death of Clive Ponting, a civil servant at the Ministry of Defence who leaked papers to an MP about the sinking of the Belgrano during the Falklands war. This took me back to 1985, when he was acquitted by a jury of breaching the Official Secrets Act, even though the judge had effectively urged them to find him guilty.

His acquittal came as a great relief to me because The Observer, of which I was then the Editor, had quoted from secret documents provided by Ponting about the sinking of the Belgrano, in which 323 people had died, and I didn’t want to find myself in the position of the Editor of the Guardian the year before. He had published documents provided by another civil servant, Sarah Tisdall, about the deployment of cruise missiles in Europe, and she had ended up in jail, which nagged at his conscience for the rest of his life.

Another reason I was so relieved about Ponting’s escape is that the jury had rejected the case of the Crown prosecutor that “the public interest is what the government of the day says it is.” That was an important victory for freedom of the press, effectively saying that the media, or indeed anyone, was entitled to express an opinion on where the public interest lies.

The sinking of the Belgrano was a mystery at the time. Was it sailing away from the 200-mile exclusion zone imposed by Britain – as the papers passed on by Ponting suggested - or, as Mrs Thatcher told the House of Commons, was it “steaming towards” the British fleet?

The truth is neither and both. The papers Ponting gave to Tam Dalyell MP described its move out of the zone, which Mrs Thatcher had been wrongly briefed about, but there was later evidence to show that this was a feint and that the cruiser always planned to return to the battle.

Some years later I met an Argentinian newspaper editor who was visiting Majorca and I asked him what he thought about the Belgrano, expecting him to say that its sinking had been a war crime. He surprised me by saying the opposite: that it was definitely heading back into battle and was therefore a legitimate military target.

The other jolt came last week when an old friend tipped me off that I had been mentioned by an article in my old paper. This story went back even more than 35 years, to the US and British-backed coup that overthrew Mossadegh, the Prime Minister of Iran, in 1953. The article said “the background to the 1953 coup has been the cause of international suspicion and conjecture.”

It disclosed that the American CIA and the British MI6 had been deeply involved in the coup. My initial reaction was that this was hardly news. The CIA-MI6 involvement in the coup has been known about for decades. A friend in MI6, who had been involved himself, had told me about in 1966. This had not been a matter of “international suspicion and conjecture”, but an established fact for a number of years.

The reason for the new story was to preview a documentary, called Coup 53 and starring Ralph Fiennes, that is being shown in Britain next week. The documentary has “discovered” an Observer article published in 1985, while I was the Editor, containing an interview with an MI6 agent called Norman Darbyshire.

In it he describes the dirty tricks used by the intelligence service, in partnership with the CIA, to get Iranian crowds onto the streets to call for an end to Mossadegh’s rule. It didn’t mention the $1 million bribe given to the Shah by the CIA to turn a blind eye to the coup.

The emergence of The Observer article of 1985 was presented as some sort of scoop when all that was needed was to look in the paper’s archive.

The maker of the new documentary, an Anglo-Iranian called Taghi Amirani, says: “We still don’t know who leaked this [interview] to The Observer.”

Well, I can solve this mystery: the interview was simply given to us by Granada TV, so that we could give their forthcoming documentary some advance publicity. No investigative journalism was required.

The new documentary has also unearthed from Granada the film of the Darbyshire interview, which was not included in the version it aired. Neither I nor my reporter on the story knew that the Darbyshire interview had been excluded from the programme. Granada didn’t tell us.

Our guess is that after The Observer’s preview appeared, Mr Darbyshire, who is now dead, either got cold feet or was warned that he would risk being prosecuted under the Official Secrets Act and withdrew permission for Granada to show it.

The paper says I “would have been told to go no further with the story, using a state provision known as a D-notice.” According to Mr Amiirani, “this smacks of a complete cover-up of British involvement to this day.”

I’m sorry to disappoint him, but I was not served with a D-notice; I was a press representative on the D-notice committee at the time and would have known.

And you can hardly cover up something that is already common knowledge.