Dragon's Den's Peter Jones revealed how he was rushed to hospital after he "collapsed on the floor".
The 55-year-old opened up about his terrifying ordeal after a candidate delivered a business pitch about deep vein thrombosis.
Hopeful businessman Paul Westerman pitched his RBR Legflow to the dragons in a recent episode of Dragons' Den.
He boasted that his product is clinically-trialled and aimed to treat deep vein thrombosis (DVT).
Sharing his 2011 experience, Peter said: "I know that this is an issue. I was coming back on a flight from Los Angeles, and I basically ended up in hospital in Windsor with a tube in my groin.
He said how he "collapsed on the flood dead" after suffering a "massive bilateral pulmonary embolism".
His ordeal came just nine days before he was due to get married and he had injured his knee a few weeks prior.
"It was without a doubt because I wasn’t moving for a long period of time.
"Ever since, I’ve done exactly the same as you. I literally move all the time, and even when I’m sitting in this chair."
DVT is when a blood clot forms in a vein, usually in the leg.
The NHS website says: "DVT can be dangerous. Get medical help as soon as possible if you think you have DVT."
Despite being very impressed by Paul's product, he didn't invest as Paul didn't have a patent.
It was recently reported that he had a fall out with This Morning presenter Holly Willoughby after she dropped out of supporting his partner's brand.
Peter and his partner Tara were friends for over 10 years before the friendship broke down over a business argument.
Peter owned a 40 per cent stake in Dan's TV production company and Tara created her own lifestyle business she named Truly and Holly was the celebrity face for the business.
But after ad campaigns were drawn up, Holly decided to pull out of the business last minute.
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The Dragon was said to be furious, and Tara told The Telegraph: "I’m not going to pretend it was devastating. We were exceptionally close. And of course as a business, you really feel the loss of a celebrity face."
At the time Holly posted a statement to Instagram saying she was stepping back from Truly as she could not give the brand the full dedication it deserved, she said: "After much consideration, I have made the decision to step away from Truly.
"To launch a brand needs total dedication and at the moment, with so many other commitments, this is not something I feel I can do without it starting to affect my family time at home. I wish Truly all the best for the future."
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