Sir Jackie Stewart is in a London hospital after falling ill during a flight from the Geneva Motor Show.
The 71-year-old former triple World Champion is reported to have suffered chest paints and passed out.
"I've just spoken to him in hospital. He seemed absolutely fine but obviously something happened and we need to establish what, but I'm on my way to see him right now," his son Paul told the BBC.
The Scottish newspaper Daily Record said the plane was met by paramedics at Heathrow airport on Wednesday. The Mirror said he was taken to Hillingdon in west London.
British Airways confirmed: "Our flight crew requested a priority landing so that a male passenger could receive medical attention immediately on arrival."
New Toro Rosso 'Ridiculously Fast': Hamilton
Two more leading F1 drivers believe Toro Rosso is set for a strong season in 2011.
The Swiss newspaper Blick recently christened the small Faenza based team's new Ferrari-powered STR6 a "Wunder Auto" after a good showing in testing.
"Toro Rosso looks reasonably strong in terms of consistency," agreed Jenson Button last month.
At an event at Dunsfold Park aerodrome on Tuesday, Button's McLaren teammate Lewis Hamilton said teams such as Renault, Williams and Force India had also produced solid cars for 2011.
"And the Toro Rosso looks ridiculously fast," said the Briton, having earlier used exactly the same description for Red Bull's pace-setting RB7.
A few days ago, Ferrari's Fernando Alonso said similarly that Red Bull-owned Toro Rosso had made "significant progress" since last year.
Hamilton added: "They could be the most interesting one to watch."
At the same time, both Button and Hamilton acknowledged the tough start to the life of McLaren's new MP4-26, reckoning that Red Bull and Ferrari are out front at present.
Red Bull's Sebastian Vettel is quoted in the German press: "Ferrari have made a very strong impression. It looks close between them and us."
As for McLaren and Mercedes, he added: "It looks as though they are having a bit of trouble."
Red Bull Eyes Nissan For Future KERS Development
One area for technical collaboration between new F1 partners Red Bull and Infiniti in future is the energy-recovery technology KERS.
In the announcement earlier this week about the 2011 and 2012 sponsor deal, the official statement earmarked "future technical collaboration" between Red Bull and Infiniti, Nissan's luxury brand.
The most obvious area for cooperation would come in 2013, when the FIA is expected to open up the KERS regulations and Red Bull can tap into Nissan's expertise in battery technology.
"I think that it is an exciting development for us," Red Bull team boss Christian Horner is quoted by racecar-engineering.com.
"Obviously the benefit of the battery know-how won't come in until 2013, whatever the regulations are.
"It opens up R+D resources on battery development which would never have previously been available to RBR as chassis maker," he added.
Lauda Tells Vettel About F1's 'Wild Dogs'
Niki Lauda has given Sebastian Vettel an entertaining insight into the "wild" behaviour of F1's past champions.
In a joint interview, new reigning world champion Vettel asked triple title winner Lauda if the reputations of some of the sport's legendary drivers as "wild dogs" off the track were deserved.
"I will tell you the truth," Lauda answered Vettel in the Red Bulletin feature.
"The best example is 1984 at the Portuguese grand prix, which was crucial for the world championship for myself and (Alain) Prost.
"My fitness guy Willi Dungl told me there was a blonde Italian woman constantly asking about me. I went to see her immediately.
"As I'm a polite person, we went out for dinner on Friday and she asked if we could eat together again on Saturday.
"I told her we couldn't eat together but she could come between 8 and 10 o'clock to my room.
"I told her I need to sleep at ten because the next day I needed to be world champion. She said okay and was gone at ten minutes before ten. I slept like a god," grinned Lauda.
He continued: "My dear teammate Prost was in the garage in the morning and was grinning to himself. I asked what he was smiling about.
"He said, can you believe it, last night I caught Stephanie of Monaco. I was relieved," said Lauda, "now it's 1-1 before god and it's time to race.
"A few hours later I was world champion for the third time," said Lauda.
He admitted that the "morality" of today's F1 stars "is maybe better".
Politician Rebukes Alonso After Speed Limit Jibe
A leading Spanish politician has rebuked Fernando Alonso after the Ferrari driver criticised a new road law.
Alonso said earlier this week that it will be "difficult to stay awake" when he returns to Spanish highways with a new speed limit of 110kph.
"To reduce fuel consumption there are other measures that are much more effective than this one," he added.
According to the sports newspaper Marca, Spain's deputy prime minister Alfredo Perez Rubalcaba hit back: "In the United States they do a maximum of 110 and I've never seen them driving whilst asleep."