A 54-year-old man was tonight arrested in connection with the disappearance and murders of five members of the Chohan family, a spokesman for Scotland Yard said.
Millionaire haulage boss Mr Amarjit Chohan (46), and his family vanished from their home in Heston, west London in February and a police investigation was launched after the alarm was raised by relatives.
Mr Chohan's body was found floating in the sea near Bournemouth Pier in April and the body of his 25-year-old wife Ms Nancy Chohan was found later in the water at Poole Bay, Dorset.
Police believe the couple's sons Ravinder, 19 months, and four-month-old Devinder, and Mrs Chohan's mother Ms Charanjit Kaur (51), were also murdered.
The man has been taken to a central London police station for questioning.