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 now, due to the enlargement of the 1994 Trademark Act, it is possible to register much more. Because of this, lawyers acting for the Princess of Wales Memorial Fund have sent 26 photographs of her to be registered with the Patent Office, in a move which could generate millions of pounds - and have huge implications for living celebrities.
The photographs cover the Princess from almost all angles, and with different hairstyles. This means that anyone wishing to use on merchandise a photograph which was "substantially similar" to any of those 26 images would have to apply to the Memorial Fund for permission, and would be liable to pay a fee.
In a concurrent move, the office is also applying to register the name Diana, Princess of Wales, as a trademark. The two moves would effectively give control of the Princess's image to the fund office, and transfer the Princess's status into that of a trading emblem.
John Major, the former prime minister, who is acting as financial guardian to Princes William and Harry, is expected to go to the High Court before Christmas to pass the trademark rights from the Princess to the Memorial Fund.
Mr Major is said to want to establish that the young princes ultimately own the image and name of their mother. The decision on the trademark application is likely to take six months.
Kate Knightley Day, of the Memorial Fund office, said yesterday: "Such an application is highly unusual. It has been prompted by the extensive misuse of likeness, which extends beyond mere photographic images."
According to Robin Fry, media lawyer at Stephens Innocent, this is an ambitious interpretation of the law, and one which may well be challenged. "It's a frightener. If people see that all things bearing this image bear trademark, and it's backed up by threats from lawyers a lot of people will capitulate. It's cheaper to buy a license and pay the 5 per cent to the fund."
Where does that leave photographers who might have compiled hundreds of their own images of the Princess? "They'd be able to use their own photographs for newspaper coverage, but it's possible that they would be blocked from using them for merchandising."
According to Mr Fry, images could still be used as long as they were illustrative - but not as a basis for making money. He referred to a recent case in Scotland, where the pop group Wet Wet Wet had registered their name as a trademark and subsequently attempted to block an unauthorised biography in the same name.
"The book was initially blocked, but it went to appeal and the judge said that was wrong, as the phrase Wet Wet Wet was being used to say what the book was about," Mr Fry said. "On that basis, you would still be able to bring out a book called Diana, Princess of Wales, with photographs, but not a photograph album.
"The most relevant thing is they're firing a warning shot across people's bows. Even if manufacturers' lawyers labour late into the night, it's not always going to be worth it."
The Diana memorabilia industry is estimated to be worth around pounds 100m worldwide. The Princess's solicitors have written more than 700 letters to companies to attempt to ensure that the memorial fund receives a share of the sale of Diana-related goods.
Recognising the lucrative possibilities of fame, celebrities are increasingly keen to take control of their image. Eric Cantona, for example, attempted to register shirts marked "Cantona 7" and the catchphrase "Ooh Aah Cantona", and Damon Hill tried to register the image of himself wearing his helmet.
"What is worrying is that instead of being used for legitimate commercial purposes, this will be used as a means of censorship. For example, in the Wet Wet Wet case they didn't like what was inside the book," said Mr Fry. "What is interesting in Diana's case is that it has come now rather than during her life."