Channel 4 stood firm last night over its decision to use photographs from the scene of the Princess Diana car crash in a documentary - despite pleas from Princes William and Harry.
The broadcaster rejected calls from the royal brothers to remove the controversial images from Diana: The Witnesses In The Tunnel, which is being aired tonight.
William and Harry's private secretary Jamie Lowther-Pinkerton wrote to the channel, appealing on their behalf.
Clarence House said that following a lack of response from the broadcaster, William and Harry felt they had no choice but to make their feelings public.
The princes believe the use of the pictures is a "gross disrespect" to their mother's memory, Mr Lowther-Pinkerton said in the letter.
He said the images were "redolent with the atmosphere and tragedy of the closing moments of (the princess's) life".
They would cause the princes "acute distress" and intruded on the "privacy and dignity of her last minutes", he said.
In his letter to Hamish Mykura, the Channel 4 executive who commissioned the programme, he asked: "If it were your or my mother dying in that tunnel, would we want the scene broadcast to the nation? Indeed, would the nation so want it?"
In a new twist, Mr Mykura, head of history, science and religion, revealed that his own father died in a car crash and said he would not object to images of his father's dying moments being broadcast if it were in the public interest.
Mr Mykura said: "I lost a parent in a road accident so I am in no doubt about the pain that can cause.
"But I do feel that if the subject had been reported in the Press like this, there are circumstances in which it would be correct for it to be broadcast, as long as it was handled in a measured and responsible way."
His father was Dr Walter Mykura, a geologist who died in a road smash in Edinburgh in May 1988, aged 62. He left a wife, three sons and a daughter.
Julian Bellamy, head of Channel 4, confirmed that the pictures would still be used.
He stressed that no images of the victims of the crash were shown in the film.
Mr Bellamy said: "We have weighed the princes' concerns against the legitimate public interest we believe there is in the subject of this documentary and in the still photography it includes."
Kevin Lygo, the director of television and content at Channel 4, said in a letter to Mr Lowther-Pinkerton yesterday many of the photographs had already appeared in the British media, including in a BBC Panorama documentary. He said: "What you are asking us to do would create a dangerous precedent in that it would have a serious impact on the legitimate and important ongoing coverage by news programmes and in documentaries of high profile tragedies like 9/11 and the 7/7 bombings, or accidents in which public figures have died, where there is the entirely responsible use of archive stills or footage depicting the immediate aftermath of the tragedy but where the dead or dying are, quite rightly and in accordance with regulatory provisions, not shown or identified."
Liberal Democrat culture, media and sport spokesman Don Foster defended Channel 4's stance.
"Most commentators who have actually seen the programme praise it for the sensitive way it deals with a very delicate issue," the MP said.
"Editorial decisions should not be made by ill-informed media hysteria but in the public interest and within existing broadcasting codes."
But the Tories condemned the inclusion of the pictures.
Hugo Swire, shadow culture, media and sport secretary, said: "This is an unprecedented intervention from the Royal Family and illustrates just how distressing the princes find Channel 4's use of these images."
Media watchdog Ofcom has received 17 complaints about the documentary but it is only within the regulator's powers to investigate a programme after it is aired.
The inquest into the deaths of the princess and her boyfriend Dodi Fayed, who died alongside her, has yet to start in full following a series of setbacks.