By Alison Freeman BBC News, London

Nina Barough was diagnosed with breast cancer in 1997

The 50-year-old founder of charity Walk the Walk had not been touched by the disease when she decided to walk the New York marathon route in her bra with a group of friends 10 years ago.

She was also unaware her first 26.2 mile power walk would lead to an annual event that thousands of women take part in.

"It just seemed a fun thing to do," she said.

"I was very passionate that it should be in aid of breast cancer, I don't know why and only the Universe will know what was behind that passion, but it's just one of the magical things that have happened to me and the charity."

Lorraine Kelly lost her grandmother to breast cancer

And the fun is still one of the main aims for Ms Barough, despite the irony of being diagnosed with breast cancer herself, aged 41, in 1997, two years after her first walk. She is now clear of the disease.

The Playtex Moonwalk - a 26 mile overnight walk through London - had humble beginnings with a small number of women who could not get places in the London Marathon taking part.

But on Saturday 15,000 people will power walk around London's streets in decorated bras.

We've come a hell of a long way in eight years Nina Barough

Television presenter Lorraine Kelly, who lost her grandmother Mary McMahon to breast cancer in 1991, will be donning a her bra for the walk for a third time.

She said she has been amazed by Nina's courage and persistence.

"She is incredible, a human dynamo," Ms Kelly told BBC News.

"She's built this event up from a very effective event to a massive one that everyone, all over the country, knows about.

"The start of the event is just amazing. Everywhere you look you see women in their bras, all excited and shouting and blowing whistles. I've never seen so many thousands of women, and men, doing something together and helping one another."

Thousands of women clamour to do the walk each year

Ms Barough said walking in bras to raise money for breast cancer research made some benefactors feel slightly uneasy at first.

"[But] it's not about making women look at breasts, or making women who don't have their breasts stand out, but about making women come together in a very strong way," she said.

"We've come a hell of a long way in eight years.

"People didn't talk about it then, I remember because it affected me at the time.

"But because of all the good work the breast cancer charities have done to raise awareness and stop people who have had mastectomies from feeling like they are another species, we are able to talk about it openly."

It doesn't matter how young or rich or famous you are, you can still get cancer Lorraine Kelly

Pop star Kylie Minogue is the latest high profile figure to fall victim to the disease, aged just 37.

"Somehow we think this perfect pop princess is untouchable and we do think that about celebrities, that they're in a bubble and ill health doesn't touch them at all," Ms Kelly said.

"But it shows it doesn't matter how young or rich or famous you are, you can still get cancer."

The event continues to grow and Walk the Walk is set to create a number of daytime "Sun Walks" over shorter distances for families to take part in.

Ms Barough said: "Initially it was about raising money but over the years it has developed and become just as much about the empowerment it gives to women.

"On the night what knocks people off their feet is the sense of camaraderie... it gives me goose bumps just thinking about it."

All funds raised by Walk the Walk go to breast cancer care and research.