Wednesday's announcement came after Diana's brother, Charles Spencer, made renewed claims this month that BBC journalist Martin Bashir used forged statements and false claims to convince the late royal to agree to the interview.

The broadcaster's director general, Tim Davie, said the BBC “is determined to get to the truth about these events.” Charles Spencer alleged that Bashir, 57, made false and defamatory claims about senior royals in order to gain his trust and access to his sister 25 years ago. The claims included that Diana's phone was bugged and that her bodyguard was plotting against her. Charles Spencer has demanded an inquiry and an apology. The BBC has apologised for faked bank statements purporting to show that two senior aides were being paid for information on Diana. But the corporation has said that the documents played no part in her decision to take part in the interview.

The 1995 interview, in which Diana famously said “there were three of us in this marriage” — referring to Prince Charles' relationship with Camilla Parker-Bowles — was watched by millions of people. Diana died in a Paris car crash in 1997 as she was pursued by paparazzi.

The BBC said Bashir, currently its religion editor, is signed off work by his doctors because he is recovering from heart surgery and complications related to contracting COVID-19 earlier this year. The broadcaster said John Dyson, a former Supreme Court judge, is “an eminent and highly respected figure who will lead a thorough process”.