William and the former Kate Middleton on Monday initiated criminal proceedings under French privacy law over the pictures published by Closer magazine, as well as seeking an injunction to prevent further distribution of them.

The injunction request was due to be considered at an emergency hearing scheduled for 1600 GMT Monday.

No defendant was named in the criminal complaint but aides to the royal couple have said they want action taken against both Closer and the photographer who used a powerful telephoto lens to snap them poolside during a short break at a chateau in southern France earlier this month.

William insisted on going after the photographer in a case which has evoked painful memories of paparazzi harassment of his late mother Diana.

The former Princess of Wales died in 1997 when the car she was travelling in crashed in a Paris tunnel while trying to escape chasing photographers.

The photographer who took the pictures which have also been published in Ireland and Italy, has not been identified and Closer has refused to name him or her.

Christophe Bigot, an advocate who specialises in media law, told AFP the magazine could stick to that stance.

"In principle, a judge cannot force Closer to disclose the identity of the photographer as that would be a breach of legislation protecting journalistic sources," he said.

The law does provide for exceptions but a judge would have to show "an overwhelming public interest" in it being bypassed, Bigot added.

That appears unlikely in this case as there is no precedent for it and breach of privacy is considered a relatively minor offence.

Under French law, both taking and publishing pictures of someone without their permission is a crime theoretically punishable by a fine of up to 45,000 euros ($60,000) and a one-year prison sentence.

In practice, no one has ever been sent to prison and fines are often purely symbolic.

The royals have put their case in the hands of Aurelien Hamelle, the advocate who defended British designer John Galliano in his trial for anti-semitic insults which led to him being sacked by fashion house Dior.

Hamelle works for Olivier Metzner, one of the highest-profile legal chambers in France, which notably represented Continental Airlines when one of its engineers was blamed for the 2000 Concorde crash.

His brief will be to ensure Closer is hit with the highest possible fine as the royals seek to send a warning shot across the bows of the international media.

A prosecutor will carry out a preliminary examination of the royals' case before deciding whether to open a full investigation which could take months to come to court. William and Kate will be named in any prosecution but not required to attend court or give evidence.

By the time of any court case, the photographs, already widely available on the Internet, will have been seen by everyone on the planet who is interested.

The royals have yet to say if they will take legal action against Italian magazine Chi, which published the pictures on Monday.

Italy has similar strict privacy laws to France but the wheels of Italian justice move so slowly that it could take years for a judgement to be delivered.

In Ireland, where the Daily Star published the pictures on Saturday, the couple's only option is to make a complaint to the Irish Press Council under a voluntary press code.