One of Britain's most successful businesswomen said having an affair helped her career
She even was awarded the Commander of the Order of the British Empire (CBE) medal by the royal family in 2010 for being so successful.
However, Leith attributed her success to something rather unorthodox at the Henley Literary Festival this week - having an affair with a married man.
Leith, 75, has admitted in the past that she had a 13-year affair with the writer and husband of her mother's best friend Rayne Kruger.
While she has also previously said that she was "not proud" of her affair with a married man, she did say that it helped her succeed.
"He was invisible and he went home at night, so I could work every hour. I worked very, very hard," said Leith at the festival, where she was promoting her book "Food of Love," as documented by the Telegraph newspaper.
"I'm not saying I'm proud of the fact I had a long affair with a married man, but it did help my business. By the time I married and had children I had the business under my belt."
Meanwhile, the Daily Mail reported her saying "I was very lucky because I didn't actually marry until I was 34. I did have a very long affair with the man who became my husband. And he went home at night. So I could work every hour that God gave."
"When we finally married … it didn't half slow me down."
Leith was married to Kruger for 38 years until he died in 2002. They had two children together. Although her net worth is unknown, she still writes novels, appears as a judge on the BBC's Great British Menucontest and writes columns for various British newspapers.