The TV watchdog Ofcom said it would follow “closely” a new independent inquiry into BBC Panorama’s interview with Diana, Princess of Wales, heaping further pressure on the broadcaster over how the scoop was obtained. Ofcom said it “does not have regulatory remit to investigate” the issue under the charter but, in a letter to the broadcaster, said: “However, we think it is essential that the BBC ensures that the concerns raised about this programme are investigated thoroughly.” Its comments follow those of the Duke of Cambridge, who has given a tentative welcome to the announcement that the BBC has appointed the retired judge Lord Dyson, former master of the rolls, to lead an investigation into how the journalist Martin Bashir landed the interview 25 years ago. Prince William said the inquiry “should help establish the truth behind the actions” that led to the programme. The investigation comes after Diana’s brother, Lord Spencer, alleged he was shown “false bank statements” by Bashir that led him to introduce the journalist to his sister, which in turn led to the world exclusive interview, watched by a UK television audience of almost 23 million people. In its letter to the corporation, Ofcom said: “One of the BBC’s public purposes is to ensure that its news and factual content is provided to the ‘highest editorial standards’. It is important that the BBC holds itself to account, openly and transparently, in relation to historic allegations of failing to achieve those standards. “This is necessary to maintain trust and confidence in the BBC’s journalism and editorial practices.” It added: “Historic events can have a long-term effect on the way the BBC’s content is perceived today. Therefore, we welcome your announcement yesterday of a fully independent inquiry to be led by Lord Dyson into the events surrounding the making of the original programme, as well as the BBC’s investigation of it in 1995 and 1996. “We will follow the inquiry and its conclusions closely.” A 1996 inquiry into allegations a graphic designer was asked by Bashir to mock-up fake bank statements was conducted by Tony Hall, then head of news, who went on to become director general. It cleared Bashir of any misconduct. Details of the internal inquiry emerged after freedom of information requests were made by Channel 4 and ITV documentary teams marking the 25th anniversary of the broadcast. Spencer has criticised that first inquiry, saying he was never questioned at the time. William broke his silence on Wednesday when he said in a statement: “The independent investigation is a step in the right direction. It should help establish the truth behind the actions that led to the Panorama interview and subsequent decisions taken by those in the BBC at the time.” He is understood to be keeping a close eye on events, and thought to have been kept informed by the BBC about developments since Spencer broke his silence two weeks ago. The prince, for whom this is an intensely personal matter, is understood to be very keen to protect his mother’s legacy, and for the truth of the matter to be unearthed and any appropriate action taken if needed. Diana’s close friend, Rosa Monckton, praised William’s statement. “Any son would want to stand up for his mother in such circumstances,” she told ITV News. “But for him and for Kensington Palace to issue such a statement ... I think it shows how deeply involved he has become in this story and about how his mother was treated.” She added: “I think it’s very important that we look at it 25 years on. It did change the course of history.” Apart from a new inquiry, Spencer has also called for a posthumous apology to Diana, and a BBC donation to charities linked to her. The independent inquiry will begin straight away and seek to discover what steps Bashir and the broadcaster took to land the explosive interview, in which Diana famously said: “Well, there were three of us in this marriage, so it was a bit crowded.” The BBC has said Diana had written a note saying she did not see any false bank statements and they played no part in her decision to give the interview. On Friday, the corporation said the note, which it previously said had been lost, had now been recovered. Spencer claims he kept detailed notes of his meetings with Bashir, and alleges the journalist had played on his sister’s paranoias by claiming he had evidence her staff were spying on her. Bashir, now the BBC’s religious affairs editor, is currently signed off from work, recovering from quadruple bypass surgery and with significant complications from having contracted Covid-19 earlier this year, the BBC has said.