Hundreds of women from across the West Country are heading to the capital this weekend for the 20th Moonwalk London.
They'll join an estimated 20,000 people tonight on the night time walking marathon, to raise funds for cancer charities.
One of those is 86-year-old Mary Yeates from Clapton in Gordano who is preparing for her 14th marathon night-time walk and hopes to complete the event in around seven hours.
Mary is a retired civil servant and walks every day near her home. Her husband died of cancer 3 years ago but she says he always encouraged her to do the walk because 26 years previously he had cancer and was cured of it.
Mary has been pictured with many celebrities at the event.
In Cornwall Jo, her daughter Lucy and friend Kim were inspired to turn their walking hobby into something that would also raise money for cancer charities - a subject close to their hearts.
They also took part last year - and this triumphant photo of them has become the image used to promote the event across the country.
The tough prep has seen them walking up to 15 miles at the weekends. they say it's helped them get fitter and been good for their wellbeing.
They're in the first wave of walkers tonight expected to complete it the fastest. But it'll still be the early hours of Sunday before they can put their feet up for a well earned rest.