When Hannah Delmas was diagnosed with a rare ovarian cancer in 2020, she didn't think she'd be running a marathon just a few years later.
"With my chemotherapy, I spent a lot of time lying in bed or at home, and lost quite a lot of muscle mass through because of being in intensive care," she says.
The 25-year-old doctor will be running for the charity Young Lives vs Cancer, which helps young people going through cancer treatment and the aftermath.
Like Hannah, Chris Reid will be lacing up his running boots and taking on the iconic 26.2-mile route around London.
Chris, also 25, has a learning disability and bipolar disorder, but that hasn't stopped him from competing in running events. His latest though, for the charity Mencap, will be the hardest yet.
"I'll actually give back to the charity that's been part of my history," he says.
The organisation, he says, has supported him with things like communication, Maths, English and work experience.
Chris, who previously lived with his parents, has since moved into supported housing and the help he receives has contributed to him becoming more confident with everyday activities such as managing his own money.
'I'm not a runner'
Hannah graduated early from medical school in 2020, because of the Covid pandemic, to help "ease some of the pressures on the NHS".
But she was then hit by the news that she had a rare ovarian tumour, having to pause her career to start chemotherapy.
After several rounds of treatment, surgery and a stay in intensive care to remove the tumour, she was back caring for patients six weeks after her final treatment.
Then, between work and follow up check-ups, she signed up to run the marathon despite her lack of experience in running.
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"I'm not a runner, I think I've ran once in primary school and secondary school, but I've never really done much since."
There have been challenges in training, such as building up fitness levels after intensive treatment, and her busy schedule as a doctor.
Another challenge was finding sportswear that didn't rub on her scars from her surgery.
"I think my preparation probably could have been a little bit better. But it's now too late."
Chris, on the other hand, feels he is more than ready, with his prep ranging from light 5k park runs on Saturdays to a training programme of 16 weeks.
But he emphasises it's not just about the running, as his nutritional diet of "brown rice, eggs and avocado" is just as important.
Chris was inspired to get into running because of Sir Mo Farah's double gold medal-winning performances at London 2012.
His first run after seeing Sir Mo's success was tough and incomplete, but he persevered after a friend encouraged him and told to "keep on going".
He says running and taking in the air "clears things out" of his head and helps his mood.
And while some may be worried about completing the marathon, Chris confidently says he'll channel his inner Mo Farah and "be able to complete it".
Crossing the finish line is what Hannah is looking forward to most.
"Just having the relief of finishing and knowing that I've completed a marathon as well as seeing everybody else at the finish line."
For people in a difficult situation like Hannah has been in, she says it's important "to take it one day at a time".
"Make little goals that you can complete because I know how frustrating it is to finish treatment, and then think it's fine for everything to go back to normal."
"Don't give up on your dreams and keep going even through tough times," Chris adds.