Princess Diana, her brother and the questions about the Martin Bashir interview

Confidence is crucial. It has to be established to entice a big name to give a candid TV interview. It is also, of course, the basis of many a scam. Pulling off a confidence trick commonly involves first offering your “mark”, or target, something useful, in an open-handed way, to build up trust, before going in for the kill.

The BBC and its journalist Martin Bashir now both stand accused, once again, of perpetrating this kind of con on Diana, Princess of Wales and her brother, Charles Spencer, to set up Bashir’s sensational Panorama interview in 1995: the programme that fully exposed the discord at the heart of the most famous marriage in the world.

What’s worse for the BBC, Lord Spencer has now also alleged the corporation deliberately covered up its failings when the incident was first looked into. Spencer wants the BBC to accept “the full gravity of this situation” and is demanding a formal inquiry into the deceptions used – recently re-examined in a Channel 4 documentary – and into the “whitewash”.

Leading figures in British broadcasting are backing his call for an independent investigation into the whole affair. On Friday the ex-ITV executive Stewart Purvis, formerly of Ofcom, said: “I don’t see why the investigation shouldn’t start immediately, because the key issue is whether the BBC did originally reach out to Lord Spencer.”

When Diana, in a dark skirt suit and dark mascara, took her seat opposite Bashir that Guy Fawkes Day 25 years ago, she was to change the way the monarchy would be seen for ever. It was a public event, but it was personal too. It was the interview that was to open the final lurid chapter of a royal romance that had begun in 1981, with her lavish fairytale wedding to the Prince of Wales, and which is now all to be re-enacted on television screens later this month in the fourth season of The Crown. So was this dramatic encounter in Diana’s Kensington Palace apartment, later watched by 23 million viewers, really leveraged by deceit and even forgery?

Back in 1996, a year before Diana’s death, Spencer – himself a former TV journalist – claimed Bashir had initially approached him with fraudulent bank statements indicating he had a mole in his security staff.

“If it were not for me seeing these statements, I would not have introduced Bashir to my sister. In turn, he would have remained just one of thousands of journalists hoping that he/she had a tiny chance of getting her to speak to them,” wrote Spencer in a letter of complaint, seen by the Daily Mail. But now Spencer also claims the BBC journalist indicated he had evidence of much more, including secret service surveillance, something Purvis regards as “much more serious”.

“I can’t believe the new director general of the BBC would not want to get to the bottom of that one way or the other,” he told Martha Kearney on Radio 4’s Today programme.

When the issue was first investigated by Tony Hall – then a BBC news executive and later the corporation’s director general – Bashir was cleared of wrongdoing. Key to that ruling was a handwritten note from the princess in which she appeared to explain that she would have spoken to Panorama without any alleged chicanery. Then 34 years old, she was nearing the end of the “War of the Waleses”, and so it was credible that she would be eager to finally speak out. She had endured “Squidgygate”, the tape released by the Sun of her conversations with her close friend James Gilbey, known by his pet name for her. She had also survived her husband’s confessional interview with Jonathan Dimbleby and the ignominy of the publication of the text of a taped clandestine phone call between the Prince of Wales and his lover, Camilla Parker Bowles.

But even so, looking back, this note, whatever its provenance, still appears irrelevant to Jason Lewis, one of two Mail on Sunday…