A 35-year-old man has been arrested by police investigating claims that Pippa Middleton's iCloud account was hacked.
Scotland Yard said officers arrested the man on Saturday evening at an address in Northamptonshire.
Pictures of the Duchess of Cambridge and her children, Prince George and Princess Charlotte, are reportedly among 3,000 images taken from Kate's sister.
Police said that the man had been taken into custody at a south London police station after being arrested on suspicion of a Computer Misuse Act offence.
Private photographs were said to have been offered to The Sun and Daily Mail newspapers via encrypted messaging service WhatsApp.
The Sun said it had been approached by someone using a pseudonym and asking for £50,000 within 48 hours.
The alleged theft comes two years after a host of celebrities, including Hollywood star Jennifer Lawrence, fell victim to a hacker attack on the iCloud - which stores private photos from phones and computers online - which saw images posted online.
In July it was announced that Miss Middleton would marry her financier boyfriend, James Matthews in a society wedding in 2017, with William and Kate saying they were a "wonderful couple".
Hedge fund boss Matthews got down on bended knee during a trip to the Lake District after they had dated for less than a year.