A French female photographer could face a year in prison and a magazine could be closed following the publication of topless pictures of the Duchess of Cambridge on holiday.
Valerie Suau, from the newspaper La Provence, is being questioned after images of Kate Middleton sunbathing sparked public outrage when they appeared in France's Closer magazine.
Suau has been placed under formal criminal investigation.
Mondadori, which publishes the magazine, and La Provence, which featured photographs of the Duchess which did not involve nudity, are similarly under police investigation.
Each could be fined up to 45,000 euros (£38,350) if found guilty and the publications could be closed for up to five years.
'The photographer and legal representatives of both companies have been questioned concerning the photographing of a person on private property and the criminal use of these images,' a spokesman for the prosecutor in the Paris suburb of Nanterre said.
'The maximum penalty for this kind of offence is one year in prison and a fine of 45,000 euros for individuals.
'For corporate bodies, the fine is 45,000 euros, cessation of business for five years and public notification of the decision.'
Kate, 31, and 30-year-old Prince William took legal action against Closer in September, as their lawyer, Aurelien Hamelle, described the Duchess as a 'a young woman, not an object’.
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He said the royal couple had suffered a 'grotesque breach of privacy' and felt 'violated' during a 'highly intimate moment during a scene of married life'.
Ms Suau, whose name is pronounced 'sewer', has kept a low profile ever since the case, but police are believed to have arrested her earlier this month.
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She took the photos on September 5 as the couple relaxed at Viscount Linley's retreat, Chateau d'Autet, in Provence.
Referring to Princess Diana's death in 1997, Mr Hamelle said it was 'just six days after the 15th anniversary of the cynical and morbid hunt which led to the death of William's mother'.
Mr Hamelle told the court William and Kate could not have known they were being spied on and a photographer would have needed a long lens, even if he or she was on a public road.
Controversial images: The French magazine Closer showed topless pictures of Kate in an issue last September
Mr Hamelle said that if the original digital images were not handed in, the Mondadori group - which publishes Closer - should be fined £8,000 a day for non-compliance.
The Duke and Duchess also launched criminal proceedings against the then unnamed photographer under France's strict privacy laws.
The French media are protected from having to name their sources - including photographers - but the royal couple are said to have made it a personal crusade to discover who took the images..
Photography spot: Some pictures were shot from a public road on a hill less than half-a-mile from the former hunting lodge, close to the medieval village of Viens, although it is possible to get closer on foot
Ms Suau has denied being responsible for taking any indecent images. She says she took pictures of Kate in her swimsuit but not topless.
Yet, despite her claims, no other photographer has been identified, nor even been placed in the area at the time.
Delphine Pando, representing the magazine, told a court case in the Paris suburb of Nanterre last year that topless photographs were no longer considered shocking.
Past: Referring to Princess Diana's death in 1997, Mr Hamelle said it was 'just six days after the 15th anniversary of the cynical and morbid hunt which led to the death of William's mother
She denied that the chateau was inaccessible to public view and claimed the magazine did not hold the rights to the pictures, so it could not be proved that it intended to republish them.
Ms Suau, who lives close to Chateau d'Autet, deep in the Provence countryside east of Avignon, told friends there was no sign of British or French police anywhere, so allowing 'any photographer who wanted' to take images.
Some were shot from a public road on a hill less than half-a-mile from the former hunting lodge, close to the medieval village of Viens, although it is possible to get closer on foot.
The road, and nearby path, offers clear views of the Chateau's raised swimming pool and its sun loungers, where Kate and William spent most of their four day break.
It was from here that a set of intimate images were captured and later published in the French Closer magazine, which is now being sued by the couple for invasion of privacy.
Ms Suau produced one set of pictures on Friday September 7th - the day the couple left. This is the same day that the Closer pictures were taken.
She aimed her camera at the pool at around 1.30pm, where she saw William wearing just a pair of swimming shorts and sunglasses as he read his I-pad. Kate, meanwhile, was in a bikini.
No British newspapers printed the pictures, which also appeared in Italian gossip magazine Chi - Closer's sister magazine - and the Irish Daily Star.
A Paris prosecutors source confirmed that 'a female photographer' working for La Provence, and 'the publisher of Closer' had both been placed under formal criminal investigation over the topless pictures.
A spokesman for St James's Palace said: 'The ongoing legal process is a matter for the French authorities.'
La Provence refused to comment on the investigation but said said Ms Suau had its 'support in the legal challenge she is facing today', the BBC said.
Mondadori, an Italian publishing group owned by former prime minister Silvio Berlusconi, said it was 'not aware of anything new with respect to what is already known about the issue.'
William and Kate were said to have been angered by the intrusion into their privacy and the magazine and photographers involved were left in no doubt about their feelings when a strongly worded statement was issued by St James's Palace last year.It said: 'The incident is reminiscent of the worst excesses of the press and paparazzi during the life of Diana, Princess of Wales, and all the more upsetting to the Duke and Duchess for being so.'