City millionaire's body lay in his flat for three weeks

Mark Clayton - a director of global investment firm CrossBorder Capital - was found dead in his £400,000 Paddington apartment after frantic relatives called police to say they could not get in touch with him.

An inquest was told he had resigned from his job and split from his girlfriend but was not thought to be suicidal. Westminster coroner's court heard the troubled Oxford graduate had been in the Priory Clinic in February after sustaining head injuries in drinking binges in London and Las Vegas.

The 38-year-old, originally from Manchester, had been admitted three times to the private hospital, where he was treated for depression, anxiety, alcohol dependency and drug problems.

He had been diagnosed with bipolar disorder and prescribed anti-anxiety drugs.

But psychiatrists said he had never had suicidal thoughts and was on the road to recovery.

Mr Clayton's family called police on 11 June after their calls had gone unanswered. He had also missed a psychiatrist-appointment on 6 June. Officers broke into his flat in Norfolk Place after noticing "a distinctive smell" and found his badly decomposed corpse in a bedroom.

There were blood stains in the living room and kitchen but the death was not suspicious, police said.

There was no suicide note and no sign of injury or a struggle. Pathologist Dr Michael Osborn, who carried out the post mortem, said he was unable to find any cause of death.

Recording an open verdict, deputy coroner Dr Shirley Radcliffe said: "Sadly it is not possible to say why he died. Whether it was medication, high alcohol intake or an arrhythmia in his heart we will never know."

Michael Howell, a director of Cross-Border Capital, said: "Everyone who worked with him is deeply saddened."