Sir Chris Hoy has revealed his “selfless” wife kept her multiple sclerosis (MS) diagnosis a secret as they dealt with his cancer treatment.

Sir Chris, one of Britain’s most successful Olympians, revealed his terminal prognosis last weekend, after announcing in February that he had been diagnosed with cancer.

According to an extract from his memoir, All That Matters: My Toughest Race Yet, published in The Sunday Times, Sir Chris, 48, praised his wife Sarra for her unwavering support while facing “this absolute crisis in the midst of my own”.

He recalled that she went for a routine MRI – seven days after his cancer diagnosis – for doctors to investigate a tingling sensation in her face and tongue.

Sir Chris said: “So whilst in a daze of shock, she went off to the scan, saying it would be a chance for her to have a lie down for an hour, joking it was as close to a spa day as she’d get. Afterwards, she continued to support me wholly and completely, leading me to push all thoughts of her MRI scan away, given her symptoms had long since disappeared.

“Then one evening in December, after our kids Callum and Chloe had gone to bed, Sarra looked serious and said she had something to tell me. I realised immediately it was something big as Sarra, always so strong in every situation, was beginning to crumble and struggling to get the words out. ‘Do you remember that scan I went for?’ she started through tear-filled eyes. ‘Well, they think it might be multiple sclerosis’. I immediately broke down, distraught both by the news and the fact she’d received it without me there.

“She went on to explain they had called her and told her over a month before. It was so hard to try to compute that she had absorbed the awfulness of this diagnosis alone, without sharing it with me, in order to protect me. I tried to let the words sink in as my mind was spinning, trying to understand what had been happening to her, all while she had been accompanying me to every one of my own hospital appointments.

“As with my diagnosis, she was the one to bring me back to the present, trying to reassure me, saying: ‘Look at me, I’m fine right now, I’m here, I’m OK’.”

MS is a chronic condition that affects the brain and spinal cord and cannot be cured, but medicines and other treatments can help alleviate symptoms that include extreme tiredness, vision problems and difficulty with walking or balance.

Sir Chris wrote: “I couldn’t believe what I was hearing; Sarra, so fit and well, able and healthy, was facing this absolute crisis in the midst of my own.

“Christmas approached, and while we were trying to prepare for what at that point felt like it might be my last, she got a call from her consultant. She took it on speakerphone and we both listened. The latest scan had been worse and confirmed Sarra had very active and aggressive MS, and she needed treatment very quickly.

“I sat with tears rolling down my face as I listened to Sarra calmly telling the doctor that her husband had recently been diagnosed with stage 4 cancer and simply saying: ‘I need you to help me outrun this’. She asked some sensible, practical questions and then thanked the doctor for phoning. I couldn’t quite fathom the amount of strength she showed to be able to take this news with such fortitude.”

Sarra began receiving treatment as Sir Chris was finishing his chemotherapy in March.

He said she receives medication through an intravenous drip at hospital visits every six months.

The Olympian describes his wife as “the centre of my life”, writing: “Within a few minutes of chatting to her that first evening, on a night out in Edinburgh back in 2006, I knew there and then that she was everything I was looking for.”

The couple were married four years later and went on to have two children, seven-year-old Chloe and 10-year-old Callum.

He said in his book: “Sarra has amazed me with all that she has faced. She has supported me and encourages me every step of the way, but rarely speaks about her own symptoms.

“She tries to stay focused on the here and now and controlling what she can by staying as active, healthy and strong as she can for as long as she can… Life is different now, but I think we’ve found our rhythm. This last year has taught us that life is fragile and we must treat it kindly, even if it doesn’t do the same to us in return. After all, today might be the best we have!”