Police investigating the mysterious death of one of Britain's richest women have arrested a man reported to be her widower.

Scotland Yard would not confirm the name of the suspect, but said a 49-year-old man was arrested in south London on Monday morning on suspicion of possession of drugs.

The man was then further arrested in connection with Mrs Rausing's death and has since been moved to a "medical facility".

Police are treating her death as "unexplained" and a post mortem held on Tuesday failed to establish a formal cause of death. Investigators have said they are awaiting the results of further tests in the hope they will answer some questions.

A Met Police spokesman said: "Officers from the Homicide and Serious Crime Command are investigating, and the death continues to be treated at this time as unexplained."

A statement from the family of Mrs Rausing, whose maiden name was Kemeny, said: "Tom and Nancy Kemeny along with all of their family are deeply saddened by the death of their beloved daughter, Eva Louise Rausing.

"During her short lifetime she made a huge philanthropic impact, supporting a large number of charitable causes, not only financially, but using her own personal experiences.

"She bravely fought her health issues for many years. The family is devastated at her death and asks to be given privacy at this difficult time."

The Rausing family said they were "deeply shocked and saddened to hear of the tragic death of their daughter-in-law" and also asked for their privacy to be respected.