His mother Mary died of colon cancer at the age of 45, and anyone who has lost a close relative to the disease doubles their chance of developing it.
“As well as my mum, my grandmother also died when she was 47,” says Stephen, who lives in north London with his wife Louise and boys Harry, four, and one-year-old Frank.
“The closer I get to my mid-40s I can’t help but wonder what is in store for me and, most importantly, my children.”
Stephen had just completed a law degree at Cambridge University when his mother died in the early Nineties. She had been diagnosed only six months earlier and it was Stephen who devoted himself to looking after her.
“We thought she just had a twisted gut,” he says.
Her doctor couldn’t look us in the eye when he told us she had cancer. I became her carer. I drove her to her radiotherapy appointments, cooked for her and did the laundry
“Her doctor couldn’t look us in the eye when he told us she had cancer. I became her carer. I drove her to her radiotherapy appointments, cooked for her and did the laundry.”
When she passed away six months later Stephen decided he would make the most out of life. He ditched law for his first love of acting and after graduating from RADA started a successful career in theatre, film and television.
Colon cancer, also known as bowel cancer, is the third most common form of the disease in the UK, affecting almost 37,000 people every year.
Symptoms include bloody stools, abnormal bowel movements and unexplained weight loss. It can be treated by surgery, chemotherapy and radiotherapy and, if diagnosed early enough, a complete recovery is possible.
However as many symptoms do not appear until the cancer has developed, a colonoscopy can help detect early signs.
This 30-minute procedure involves inserting a camera into the large colon to examine the lining for abnormalities.
As around 80 per cent of cases develop in those over 60, the NHS routinely offers everyone aged 60 to 69 a home faecal occult blood (FOB) test which checks for rectal bleeding, a sign that further investigation is needed.
Stephen was introduced to the idea of having an early colonoscopy while working with actress Geraldine James.
With a history of bowel cancer in her family, she was well versed in the importance of having regular check-ups.
Stephen, his two sisters Anita and Lisa and maternal aunt have undergone checks every four years ever since.
“Having a camera put up your backside doesn’t sound very pleasant but the alternative is much worse,” says Stephen.
“I’m now upping my check-ups to every two years.”
Unfortunately Stephen’s uncle, his mother’s brother, was never tested and died from colon cancer a few months ago.
“It is heartbreaking to think they could have saved his life.”
IN 2005, by which time Stephen was already a television favourite playing self-appointed lothario Dr Guy Secretan in the Channel 4 sitcom Green Wing, his dad James was diagnosed with a brain tumour and died six months later aged 63.
“When mum was ill dad and I became incredibly close because I looked to him for support,” says Stephen. “When dad got ill, being the eldest, I became head of the family.”
He would leave filming at the fictional ward at Northwick Park Hospital in Harrow and travel to a central London hospital to visit his dad. “It was surreal to say the least.”
With two sons and a family history of cancer, it is easy to see why Stephen has become a spokesman for Bupa’s I Know Someone With Cancer booklets, a range of guides for children who have a parent or family member suffering from the disease.
The four free books: What Does it Mean?, Life at Home, Visiting Hospital and an activity book were written to help seven-to-11-year-olds understand what cancer is, what treatment is needed and how to deal with it.
They help the child understand that there is no right or wrong way to react when they hear someone has cancer and gently explain how the illness can affect loved ones, making them depressed or angry.
“When a family is faced with news that a loved one has cancer they are stuck between despair and hope and children are left wondering what is going on,” says Stephen.
“Do you keep everything from them and then months down the line suddenly tell them their mother might be dead within a week? These books help you explain everything.
“When you’ve lost a loved one you realise how grateful you are for any help in those moments and any scheme that tries to help families during that terrible time gets my backing.
“I was sitting next to both my parents when they were diagnosed. In that moment you are acutely aware you can’t start crying, as your emotional needs aren’t the priority. Similarly the parent diagnosed with cancer has to rein in their emotions because their children are looking to them for leadership.
“I’m supporting the Bupa books because they are designed to help young families in this situation.”