"He was a complete handful Into everything. Once, he shaved his brother's hair off. And he would not take 'no' for an answer. Then again, neither would I. It was a battle of wills,' the Daily Mail quoted her, as saying.
"He was a more difficult teenager. He was smoking by his mid-teens. At 15 he "borrowed" his parents' car and had a prang.
"Once they started to drive, oh my goodness. It was awful. I worried about them being in an accident. I worried about them having a drink then driving - it wasn't such a no-no then.
"I'd always told my sons that the most important thing was that they did a job that made them happy, and I knew that Simon had ambition," she said.
However, she also admitted that her son's remarkable characteristic has always been his honesty.
"His characteristic honesty made an early entrance, too. At four, when he was asked if his mother looked pretty in her new hat he retorted: 'No, she looks like a poodle,'" she added.
The 80-year-old also said that her son has always had a strong desire for achieving and going for more.
"He started working at EMI, in the post room, I remember him being horrified that there were two men there who had been doing the job for 20 years. He said to me: 'This is just a stepping stone, Mum. I want more,'" she said.
"Of course he did. Within a few years, Simon had moved in to pop management, discovering that he had an uncanny knack for spotting the stars of the future.
"I have often wondered that. He's certainly a workaholic; he gets that from his father. Eric was a huge influence," she said.
Julie Cowell is also quite firm that she won't listen to the rumours about her son's womanising ways.
"I just don't believe that. Newspapers can write what they want," she says.
She also believes that her son will eventually settle down and have his own family.
"I know he would be a wonderful father. He is brilliant with Nicholas's children, but he says that it isn't for him. I've always said that he will change his mind some day, but I'm not so sure now.," she said.
"Once Simon has made up his mind about something, that tends to be it. I'm not sure even I can talk him round this one," she said.