The Duke of Cambridge has said the publication of topless photographs of his wife in a French magazine was "all the more painful" given his mother's experience with the paparazzi.
A statement from the duke was read at the French trial of six people accused of invasion of privacy and complicity.
The images were taken as the royal couple holidayed in Provence in 2012.
They appeared in Closer magazine in France, while regional newspaper La Provence printed swimwear pictures.
Paris-based agency photographers Cyril Moreau and Dominique Jacovides are accused of taking long-lens shots of the royals, including the topless pictures of the Duchess of Cambridge, from a public road.
The others accused in the case, being heard at Nanterre, near Paris, are Closer's editor Laurence Pieau, Ernesto Mauri, chief executive of the Mondadori group which owns the magazine, La Provence photographer Valerie Suau, and Marc Auburtin, the paper's publishing director at the time.
A prosecutor urged the court to impose "very significant fines" while a lawyer for Prince William and Catherine called for "very large damages".
Paul-Albert Iweins, representing Closer magazine, said the duke and duchess were hoping to claim 1.5 million euros (£1.3m) in compensation.
He argued that the couple had been the subject of much media attention - including the broadcast of their wedding - and that the photos did not constitute a breach of privacy and cast them in a positive light.