After receiving the all-clear following surgery, Tim, 36, now wants to share his story in the hope it will inspire others to get tested.
"Two of our directors grew moustaches last year and, seeing how ridiculous they looked, I thought I'd do the same this year to raise money for charity," the father-of-two told the Evening Standard.
"The day before Movember started, on October 31, I got the call. It was confirmation that I had testicular cancer. I'd gone to see my doctor thinking it was just a normal ache and pain.
Tim, who won the BBC business show in 2005, is now the head of clients services for recruitment company Alexander Mann Solutions, as well as Boris Johnson's ambassador for training and enterprise.
Doctors told him that the tumour would have to be removed in the operating room — and breaking the news to his family was tough.
Tim has been supporting Movember to raise money for prostate cancer
"There is a fear of the word," he said. "My wife was distraught as he mother had been diagnosed with breast cancer four years ago, and my mum was devastated.
"I am a great believer in being positive. But I wouldn't have been able to get through it without the strength and support of my family."
Tim — who has two children, Kayla, 12, and Aaron, four, with wife Jasmine — had surgery at the Chelsea and Westminster hospital just over a fortnight after his diagnosis.
After leaving Amstrad Tim worked alongside Boris Johnson as his Training Ambassador
Three days after the operation he was hosting the National Apprentice Awards and shaking hands with Deputy Prime Minister Nick Clegg, the newspaper reports.
"The medical staff were fantastic," he said. "I know us guys don't like to talk about it, but I'm exactly the same as I was. Thankfully, all my bodily functions are normal. Cancer doesn't have to be a death sentence. Testicular cancer has a 95 per cent success rate if caught in time."