A man in his 60s and a woman in her 70s have been found stabbed to death at a home in south-west London.
Police were called to the address in Redfern Avenue, Whitton, shortly after 09:30 BST.
A 31-year-old man was arrested on suspicion of murder in Slough at about 15:00, Scotland Yard said.
Officers believe they know the identity of the two victims, and they are not looking for anybody else in connection with the deaths.
Ch Supt Sally Benatar, from the Met’s south west command unit, called it an “isolated incident”.
She added: “I would like to express my thanks to emergency services colleagues, including Thames Valley Police who have supported our response to this incident.”