Sir Chris Hoy's painful sacrifice to keep hair during chemotherapy for sake of his son

Cancer-stricken Olympic legend put himself through excruciating pain in order to save his hair for the sake of his 10-year-old son.

Hoy, 48, has after revealing that his condition, which he , is terminal. Doctors have told the former cyclist that he has 'two to four years' to live.

An 11-time champion, Hoy is one of Britain's most decorated Olympians; winning six gold medals and one silver across four different - Sydney, Athens, Beijing and London. Also a father to seven-year-old Chloe, the dad of two been battling cancer for more than a year but has now spoken in-depth about his painful battle.

In an interview with , Hoy revealed that son Callum asked him: "Are you going to die?" Hoy told his young boy that no one lives for ever, although he hoped that, thanks to medicine, he'd be alive for 'for many, many years'.

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Callum continually asked if Hoy would lose his hair, so for his sake and to ensure that his cancer treatment remained unknown to the public, Hoy chose to wear a cold cap, putting himself through agony. "It's like your head being in a vice," the 48-year-old explained.

His hair was saved but it was the worst pain that Hoy had ever experienced. "And I've got a very high pain threshold," he added.

During one gruelling four-hour session in round two of chemo, Hoy had a 'violent' allergic reaction. "I was absolutely broken by the end of it," he admitted. "I feel like, 'What a wimp'."

Hoy married to wife Sarra Kemp, 38, in 2010, three years before retiring. In more heartbreaking news, Hoy also reveals in his upcoming memoir, 'All That Matters: My Toughest Race Yet', that Kemp was diagnosed with 'very active and aggressive' MS around a month after he was told that he had stage 4 cancer.

"It was such a huge blow, when you're already reeling," Hoy said.

Writing his memoir and recording it in audio form was also a painful experience. "[You're] reading the words out loud, you have to connect emotionally. You've got to actually read in a way that means something," he added.

"But the risk is getting too close to it – because you're suddenly thinking, these are the words that my kids will listen to when I'm gone. And that is, without doubt, the hardest thing I've ever done.'"

Since retiring, Hoy has launched various new careers, including in motorsport, where he competed as a driver in the famous Le Mans race. He's also worked as a TV pundit on the Olympics and become an author, publishing two fictional children's books.