TV entrepreneur Duncan Bannatyne has suffered a suspected heart attack while working in his office, a company spokeswoman says.
The wealthy star of Dragons' Den was being treated at Darlington Memorial Hospital after falling ill at the headquarters of his gym company in the town.
A spokeswoman for the Bannatyne Group said: "Everyone at the company is very concerned and upset, but we know that Duncan is a very strong person and we are confident he will make a full recovery.
"Everyone wishes him well. We'd like to thank the quick and professional actions of the paramedics who attended to Duncan and thank the staff at the Memorial Hospital for his ongoing care."
Bannatyne, who lives on the exclusive Wynyard estate in the countryside north west of Middlesbrough, was born in Clydebank, Scotland and was raised in what he describes as "relatively modest circumstances".
His business interests now include health clubs, hotels, property, media and transport and he is best known as a tough-talking business angel on the BBC show Dragons' Den.
The former Royal Navy stoker began his business empire with an ice cream van, rapidly expanding that business in tough competition before setting up a chain of care homes.
On his website he says he sold that for £26 million in 1996 and his children's nursery chain for £22 million.
He has written five self-help books on becoming a success in business and managing money, was awarded an OBE for his charity works and is a vehement anti-smoker.