Hans Kristian Rausing, 49, is heir to the £4.5bn Tetra Pak packaging empire. His wife, Eva, 48, was found deceased at their home in Belgravia this week (pictured). Scotland Yard is treating her death as unexplained.
Hans is currently in hospital, where he was taken after being questioned by police who had seen him driving erratically in south London on Monday morning and made an arrest.
Though it is thought that Eva suffered a drugs overdose, pathologists could not establish an exact cause of death owing to the state of the body, which suggests she could have been dead for some time.
It is understood that the post mortem could not pinpoint a time of death, either.
Hans and Eva first met at a drug addiction clinic in the US 25 years ago. In 2008, it appeared that Eva may have succumbed to drugs again, after she was arrested for trying to smuggle Class As into a function at the US embassy.
According to reports, Hans will be in hospital for “a matter of days” owing to an unspecified illness, but remains under arrest.
Detectives are combing through CCTV footage from cameras on the house in an effort to determine when Eva was last seen alive.