Health secretary Jeremy Hunt joined more than 100 walkers on an overnight walk from St Thomas' Hospital to Guy's Hospital - via a circuitous route - to raise funds for the Dimbleby Cancer Care Charity.
This is the fourth year that broadcaster Jonathan Dimbleby has led the 50km walk which raises money for the charity set up in his father's name: Dimbleby Cancer Care.
Names from the world of politics including health secretary Jeremy Hunt, Labour's shadow health secretary Jonathan Ashworth and Lib Dem MP Norman Lamb came to St Thomas' Hospital on Friday night to support the event.
Chair of Dimbleby Cancer Care Jonathan Dimbleby said: "A little weary. Actually knackered. But wonderful night walk. And worth it. Thank you to everyone for your support. We could not do it without you."
Starting at St Thomas' Hospital the walkers headed west to Putney, onto Hammersmith Bridge before heading out Canary Wharf and down to Greenwich before finally heading back to the charity's home at Guy's Cancer Centre.
For the first time this year there was also a 25km route and 12km family option.
Jeremy Hunt, Secretary of State for Health and Social Care, who took part in the 25km route, added: "I lost my father to cancer in 2013, a year into my tenure as health secretary. Since then, I've been struck time and again by the fact that patients and families affected by cancer need much more than just medical care and treatment: they need practical and emotional care and support along the way, and Dimbleby Cancer Care is doing amazing work offering just that to people across the country.
"Their new Cancer Care map is a great example of this: a directory of services in each local area for families facing cancer, from NHS services to mental health support to practical assistance. There's often much more help out there than people realise, and organisations like Dimbleby Cancer Care offer help and support with a human touch that can make a huge difference. I was proud to take part in their annual Walk50 Challenge event this evening."
This year's event raised around £45,000 for the charity.
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