Channel 4 will broadcast photographs tonight taken at the scene of the crash that killed Diana, Princess of Wales, in defiance of a late plea from her sons to remove them.

The private secretary to Prince William and Prince Harry, Jamie Lowther-Pinker-ton, wrote to the channel saying that they felt that the images would be a “gross disrespect” to their mother’s memory.

Royal sources indicated that the letter had been written at the instigation of Prince William, who wanted to “take a stand” against intrusions into his mother’s dignity.

Mr Lowther-Pinkerton wrote to Hamish Mykura, the head of history, science and religion at Channel 4, after seeing a preview of the programme. The letter 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?”

The letter called on Channel 4 to remove images of the car with the Princess inside and of a medic treating her. “These photographs, regardless of the fact that they do not actually show the Princess’s features, are redolent of the atmosphere and tragedy of the closing moments of her life,” Mr Lowther-Pinkerton wrote.

Mr Mykura has disclosed that his own father died in a car crash in 1988, aged 62. He claimed that 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 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, Dr Walter Mykura, was a geologist. He left a wife, three sons and a daughter. Mr Mykura expressed regret that the princes felt the film to be intrusive.

Politicians also waded into the latest row to engulf Channel 4, with the Conservatives calling on the broadcaster to respect the princes’ wishes.

But Channel 4 said that it would screen the photos, which show the dying Princess receiving medical assistance.

It declined a request from Clarence House to send a copy of the documentary, Diana: The Witnesses in the Tunnel, for the princes to view. The film exonerates paparazzi from blame over the 1997 crash in Paris that killed the Princess, 36, Dodi Fayed, 42, and the driver, Henri Paul. A screening was held for Paddy Harverson, the princes’ press secretary, and Mr Lowther-Pinkerton.

Clarence House released the letter after Channel 4 failed to respond by a Monday deadline laid down by royal aides.

Kevin Lygo, the Channel 4 director of television, rejected the demand in a reply sent yesterday. He wrote: “You are in effect asking us on behalf of the princes not to broadcast this programme at all, since these photographs are crucial to the programme’s evidential arguments and analysis.” This would set a “dangerous precedent” for documentary-makers.

Hugo Swire, the Shadow Culture Secretary, said: “Clarence House have now seen the footage, and believe it to be intruding upon the privacy and dignity of Diana’s last moments. Channel 4 would be crossing the line if they chose to press ahead.”

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