Trustees of the memorial fund set up to distribute money raised in the Princess's memory are seeking to register 26 photographs of her life, from her engagement in 1981 to the landmines campaign of 1997, as trademarks, which may generate millions of pounds. If the trademark is approved it will apply to any picture or likeness of her, not just those listed.
The key is the 1994 Trademark Act, which is increasingly attracting the interest of celebrities such as pop stars, footballers and even the Teletubbies. This enables registration of a likeness or image, in addition to name and unofficial titles, to be uniquely attributed to the person in question. The Act makes it an offence to use the image, or even one likely to be mistaken for it, without prior permission, for goods.
"Any media lawyer worth his salt will be calling clients and looking into this," said Tom Ang, senior lecturer in photographic practice at the University of Westminster. "It could turn out to be Diana's revenge on photographers. All the photographic agencies around the world who thought they had copyright on her pictures may find they don't have as much free use as they thought."
The last attempt to "patent" a face was when the pop star Adam Ant tried to prevent the publication of cheap posters bearing his "New Romantic" look. The judge in that case ruled that there was no copyright on someone's appearance, but the 1994 Act has taken the ground from under the feet of the Carnaby Street-style trader using famous faces to sell mugs, T- shirts and tea towels.
The former Manchester United footballer Eric Cantonaused the new Act to register his image, his name in conjunction with the number seven (his team number), and the call "Ooh, ah, Cantona".
Other sports stars to follow the same route include Formula One champion Jacques Villeneuve, last year's champion Damon Hill, and footballer Alan Shearer. Last week the Teletubbies received a trademark for their image and pop stars Liam and Noel Gallagher have launched similar actions.
Intellectual-property lawyer Mark Stephens said celebrities had a strong case. "The key is that you, as a registered trademark, must be trading on your image. Then you can argue that you are losing out financially because others are trading off your image," he said.
"Groups such as the Spice Girls can do nothing about people taking photographs of them and using them in the papers, even though they get so miserable about it. It won't affect news coverage because using photographs on such a basis is not using them primarily for profit."
Mr Ang was more cautious. The Act may even provide politicians and other public figures with a form of censorship, he said. "The grey area is where the trademark could be bought into disrepute. Neil Hamilton may struggle to win a case if Have I Got News For You has a go at him because it could be said to be fair comment but John Major may have a case against his Spitting Image character."
The concern has already been raised after news that Mishcon de Reya, the law firm acting for the Diana fund, is attempting to block the production of a TV film about her life. Mishcon de Reya has threatened legal action against Mirror Television over its attempts to make a film called People's Princess without permission from Diana's estate.
Kelvin MacKenzie, Mirror Television's managing director and executive producer of the film, said the project would go ahead and described the lawyers' move as "outrageous".
But the lawyers acting for the estate are making the right move, according to Mr Stephens. "It will enable charities which would have benefited from her during her lifetime to continue to benefit. The fund also has a legal obligation to maximise the amount of money for the Trust."
The price put upon an image usually makes the effort of trademarking worthwhile. Elvis Presley Enterprise, which controls the singer's estate, is thought to be worth at least pounds 160m, with annual earnings of pounds 45m.
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