A former soldier who was medically discharged with PTSD is set to finish a gruelling 10 consecutive marathons in Hyde Park, London, taking just 100 hours, all in aid of saving a young girl from a rare and life-threatening disease.

Experts have warned that his latest challenge will take more than six months for his body to recover.

Darren Hardy, who served in the British Army for 15 years, started his challenge at 8am last Wednesday in Manchester before running south to London, where he plans to complete the London Marathon course to mark the finish of his challenge.

The 36-year-old from Fleet said he was inspired to take on the feat to raise money for 13-year-old Aggie Candy-Waters, who suffers from a neurodegenerative condition called H-ABC – a severe form of TUBB4a leukodystrophy.

For Aggie, and thousands like her around the world, there is hope for a treatment, yet without vital fundraising from people like Darren, there is a chance that the medications under development will not be ready in time.

“I’m not embarking on this light-heartedly,” he said. “I’m going to need to draw on every ounce of motivation and determination to make it through.

“I am fascinated about testing the limitations of the human body, but this one is going to truly hurt.”

Hardy is no stranger to extreme endurance challenges.

Last year, he ran 131 miles (211km) along the south coast and broke two world records by pulling a car.

He said: “After the south coast challenge I was ruined for months, so that puts the enormity of this into context.”

“I got to know Aggie and her family last year, and we formed a deep bond,” Hardy said. “I felt angry and frustrated that more couldn’t be done. The injustice of her condition and the lack of a treatment just hit home.”

“That’s when I found there was hope. There were people around the world working on a treatment, but there just wasn’t the funding to complete it.”

“Ever since then I’ve done whatever I can to help – even putting my body on the line.”

“A massive part of the motivation to get to the finish line is the knowledge that every step I take is helping Aggie and children like her live a longer, more fulfilled life.”

As part of his mission, Hardy will also visit three young H-ABC patients, and biotech company SynaptixBio, which is developing the treatment for TUBB4a leukodystrophy.

“Darren is a modern-day superhero,” says Ali Candy Waters, Aggie’s mum. “He’s willing to risk his own health and push his body to the absolute limit – all to help our little girl.

“We really can’t thank him enough, and hope that the country gets behind him.”

He is taking on this challenge with the support of Lane Intellectual Property, who stepped in last minute to cover the challenge costs to enable this immense fundraising feat.

Darren is undertaking his challenge with the support of Resilient Nutrition, Precision Fuel & Hydration, Ollie Ollerton’s Battle Ready Fuel, Break-point, and Toro Pro.

Having been medically discharged from the army with PTSD in 2017, Hardy’s mental health saw him on the verge of taking his own life.

Saved by the support of his family and training for ever more extreme physical challenges, Darren regularly refers to his bid to push human performance further than ever as “his therapy”.