Allen Carr the man who went on to help millions of people to give up smoking after giving up his 100-a-day habit - has died from lung cancer.
The 72-year-old was at his home near Malaga in Spain and his family were with him, a spokeswoman said.
Friends said it seemed probable that the years he spent curing smokers in smoke-filled sessions at his clinics may have contributed to the illness.
Mr Carr started his career as a qualified accountant in 1958. He was successful in his chosen profession, but his cigarette addiction was driving him to despair. He developed his Easyway method of giving up smoking in 1983 and set up a clinic in south west London.
He went on to build an empire of 70 clinics in 30 countries which treated 45,000 people last year. Aside from his tips on how to give up smoking, Mr Carr gave advice on how to stop drinking and lose weight.
He sold more than 10 million copies of his books and DVDs worldwide. His first book, Allen Carr's Easyway To Stop Smoking, has sold more than seven million copies. John Dicey, worldwide director of Allen Carr's Easyway, said today:
"This is a tragic and emotional day for everyone involved with Allen Carr's Easyway organisation, most of whom, as former smokers, owe Allen their lives.
"Our hearts go out to Allen's family and the millions of former smokers who will be saddened by his passing.
"The fact that a former 100-a-day smoker, having quit in his middle age, lived to the ripe old age of 72 is a tremendous message to all smokers.
"Allen Carr's refreshingly different approach to stopping smoking earned him the position as the world's leading expert on helping smokers to quit.
"He was an iconic figure and a real inspiration and we will celebrate his life's work by ensuring that Allen Carr's Easyway message and method continues helping smokers quit throughout the world."
Mr Carr is survived by his wife, Joyce, his four children, two step-children, 11 grandchildren, and one great-grandchild.