The Duke of Cambridge has blasted the decision to publish topless photographs of his wife as “particularly shocking” in court.
William claimed the publication of images of Kate sunbathing on holiday in the south of France mirrored his late mother’s battles with the paparazzi.
The Duke expressed his sadness at the incident more than four years ago in a written statement read to a court in Nanterre, west Paris, where six people are on trial in connection with the alleged breach of privacy.
The long-lens images of Kate, taken as they holidayed in the south of France, adorned the front and inside pages of France's Closer magazine in September 2012 alongside an article about the loved-up pair entitled "Oh my God!".
William and Kate were on the terrace of a private chateau in Provence owned by Viscount Linley, the Queen's nephew, when they were photographed.
The trial of six people - including three photographers - linked to Closer magazine and regional newspaper La Provence began on Tuesday.
In a written declaration read in French in court by the couple's lawyer Jean Veil, William said: "In September 2012, my wife and I thought that we could go to France for a few days in a secluded villa owned by a member of my family, and thus enjoy our privacy.
"We know France and the French and we know that they are, in principle, respectful of private life, including that of their guests.
"The clandestine way in which these photographs were taken was particularly shocking to us as it breached our privacy."
He added that the images were "all the more painful" given the harassment linked to the death of his mother, Diana, Princess of Wales.
William ended his statement by thanking the French authorities for their support and work on the investigation.
Ernesto Mauri, 70, chief executive of publishing group Mondadori which produces Closer, faces one charge of using a document obtained by a breach of privacy, as does Marc Auburtin, 56, who was La Provence's publishing director at the time.
Laurence Piau, 50, editor of Closer magazine in France, is charged with complicity.
Agency photographers Cyril Moreau and Dominique Jacovides and Valerie Suau, who was a photographer for La Provence, stood in the dock together as they faced charges of invasion of privacy and complicity.
The three other defendants were represented in court by lawyers.
The court heard that cellular data placed photographers Moreau, 32, and Jacovides, 59, in the areas surrounding the chateau between September 4 and 6 when the topless images are believed to have been taken.
While the pair acknowledged they were looking for the royal couple, they said they did not know where they were staying.
Both deny taking the photographs at the centre of the controversy, which are alleged to have been sold on to Closer.
Suau, 53, who is said to have taken photographs of the Duchess of Cambridge in her swimwear which were printed in La Provence, told the court she did not intend to breach the royals' privacy.
The publication of the images prompted a fierce reaction at the time, with a statement issued by St James's Palace stating they were "reminiscent of the worst excesses of the press and paparazzi during the life of Diana, Princess of Wales".
The royal couple launched their own legal proceedings in 2012 and a court in Paris banned Closer, which is separate from the UK's Closer magazine, from printing any further images.
Presiding judge Florence Lasserre-Jeannin will announce the verdict on July 4 at the Tribunal de Grande Instance de Nanterre.