Buckingham Palace’s annoyance at the BBC’s misleading promotional clip of the Queen at her photo session is as nothing to the event in 1995 at which relations between the monarchy and the corporation reached their nadir.

When Diana, Princess of Wales, gave Martin Bashir, of Panorama, her famous “three people in this marriage” interview, relations between the state broadcaster and the head of state were already uneasy.

A BBC employee had leaked the text of the Queen’s 1992 Christmas broadcast to the press; she took The Sun, which published the full text, to court for breach of copyright and made it donate £200,000 to charity. Bashir and the Princess filmed their interview in considerable secrecy. She did not even tell her own press officer, who resigned as a result. The Princess decided that the one person who must know in advance was the Queen, and she telephoned her former mother-in-law a week beforehand. John Birt, then the director-general, was also in on the plot, and debated whether to tell Marmaduke Hussey, the BBC Chairman. The Princess herself did not want the chairman told in advance for fear that he would pull the plug on it.

Mr Birt decided that his chairman would have to know. Hussey was informed at the same time as the Queen, and was incandescent. Not only was he a staunch monarchist, but his wife, Lady Susan, was a lady-in-waiting to the Queen. He regarded the interview almost as treason but did not prevent its transmission, largely because he failed to persuade the other BBC governors to share his ire.

The Palace greatly disliked the interview, viewing it as fuel on a raging fire of bad publicity surrounding the heir to the throne and his estranged wife, which was damaging the reputation of the monarchy. But it could do nothing; the interview broke no rules — except perhaps those of taste — and breached no copyright.

But the Queen can get her revenge in small, telling ways. ITV was given responsibility for producing the Christmas royal broadcast for three years.

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