The Metropolitan Police were working with hospital doctors yesterday to try to discover the circumstances behind the sudden collapse of the Prime Minister’s top intelligence adviser.

Alex Allan, 57, the chairman of the Cabinet Office Joint Intelligence Committee, has been in a coma since he was found lying unconscious at his home in West London on Monday.

Police are trying to find out what Mr Allan was doing over the weekend, and whether he had been lying unconscious for some time before a tenant who had his own key to the house found him on Monday morning and raised the alarm.

A spokeswoman for the Metropolitan Police said that the matter was being treated “as non-suspicious at this time”, adding: “We are working with the hospital to discover the exact circumstances of his illness.”

Mr Allan, who lost his wife, Katie, to cancer last November, was taken to Hammersmith Hospital, near his home, and has been subjected to a number of tests, including toxicology analysis. The hospital referred all calls to the police.

Mr Allan, who was a keen jogger, was described yesterday as being “in a very bad way”. It is understood that his mother, brother and sister are with him in hospital. The Metropolitan Police have assigned a liaison officer to assist the family. Mr Allan has no children.

The news of his collapse shocked Whitehall colleagues. They said that there had been no prior warning of any serious health issue, although Mr Allan had told friends that he was feeling a little off-colour at the end of last week. There had been some expectation that he might not come to the office on Monday morning. “But as the Government’s former e-envoy \, he is a master of the internet and was quite capable of working from home,” one official said.

It appears that although he had not turned up at the office on Monday morning, there was no alarm among colleagues. The first report that something had happened came with a phone call from the tenant who rents the top floor of Mr Allan’s house.

“We’re currently in limbo. We don’t know what happened,” an official said.

The police examined his home computer and found that he had been browsing his favourite website, dedicated to the American rock group the Grateful Dead, of whom he is a longstanding and devoted fan.

Mr Allan was appointed chairman of the Joint Intelligence Committee (JIC) last November. The JIC is the most senior body advising the Prime Minister on secretly acquired intelligence material relating to defence, foreign affairs and the global economy.

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