Hans Rausing, one of the richest men in Britain and heir to the Tetra Pak drinks carton empire, has been arrested in connection with his wife's death after her body was found at their home in Chelsea in west London.
Her death was being treated as unexplained.
Mr Rausing had earlier been detained by police on suspicion of possessing drugs.
More top news
Ed Miliband has pledged to give zero-hours workers the right to convert their contract into a regular job after three months.
More than 100 leaders have declared their support for a Conservative-led government, warning a Labour would "put the recovery at risk".
The winds will remain strong tonight and in the north showers will continue, which may turn wintry over high ground.