Jackie McCarthy tried for years to have a baby and put her lack of success down to fertility problems.

But after a series of unexplained illnesses, the news doctors delivered was the last thing she expected – she had cancer. Worse still, it was incurable stage 4 lung cancer.

It was a devastating double blow for the Surbiton woman.

Despite the bleak news, Mrs McCarthy says, terminal diagnosis aside, she is happier than she has ever been.

This despite the fact that she was diagnosed on her 44th birthday.

“I was shocked, devastated, frightened – just in disbelief,” Mrs McCarthy said.

“Most of all, I was sad for the life I wouldn’t lead. I was having IVF at the time so my life plan changed overnight.”

During her first attempt at IVF, she was thrilled to find she was pregnant. But sadly, she miscarried.

It was a crushing blow and it took her nine months “not to cry randomly.”

Jackie started treatment immediately and in the last three years she has had 13 cycles of chemotherapy and radiotherapy five times.

Now her kidneys no longer function properly so her future treatment options are limited.

The illness and ongoing treatment has allowed her to enjoy time with her partner Mark, her friends and her cats Jasper and Sapphire. She is determined to get on with her life.

“I’m now ‘up’ most of the time, rather than down,” she said. “I think having a positive mental attitude is very important. I think if we worry about the disease all the time, we’d be much worse off, so I try to just get on with it and ignore it. Ninety-nine per cent of the time I’m smiling.

“I try not to think about the future too much and concentrate on today. And I find helping and mentoring other people helps my own happiness.”

Despite all this, she has found the strength to pick herself up and become an advisor and mentor to other cancer patients, passing on information and useful tips she has learned during her extensive and ongoing treatment.

Jackie, 47, will be guest of honour at Cancer Research UK's Race for Life at Hyde Park on Sunday, July 23.

Jackie’s own symptoms were missed for years so she is passionate about early diagnosis.

“Early diagnosis is so important," she said.

"Many people might not look ill if they have cancer – I still don’t look particularly ill. That’s why it’s important to raise awareness about the signs and symptoms of cancer. If you feel sick or notice anything unusual about your body – go to the doctor. If you still aren’t happy – persist."

Jackie will be speaking to the crowd and firing the starting gun at Hyde Park Race for Life, to do her part to help bring forward the day when all cancers are cured.

Go to raceforlife.org