Chris Tarrant is recovering following a stroke he had during an 11-hour flight.
The ''Who Wants to Be a Millionaire?' host was rushed to Charing Cross Hospital in west London from Heathrow Airport after falling ill on a plane from Burma.
His agent and manager, Paul Vaughan, told The Sun newspaper: "The doctor describes it as a mini-stroke, probably brought on by the asthma and bronchitis on the plane. They found a clot which they managed to break up.
"It was a clot in the leg and that can immediately go to the brain or lungs."
The TV veteran is being looked after by the same consultant who cared for BBC news presenter Andrew Marr, who had a huge stroke in January last year.
Chris, 67, was returning from filming a fishing show in Burma on March 1 when he fell ill and has since started to make trips to his London flat but is yet to return home on a permanent basis.
His agent added: "He is determined to leave hospital. But he's not going back to work. This is a nasty wake-up call."
Doctors reportedly first thought the star had an asthma attack before discovering a potentially fatal blood clot in his leg.
He underwent emergency treatment to destroy it before it could dislodge and put his life in further danger.
Chris recently finished filming 'Who Wants to Be a Millionaire?', which ended after 16 years on air last month.
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