Two friends will walk non-stop for 30 hours from London to Brighton.
Jo Ellis, 38, and Edward Harris, 28, will take on the 100km trek in memory of their late colleague, James Aldis.
They aim to raise £2,000 for the Royal Marsden Hospital (RMH) Cancer Charity, which took care of James, of Lyndhurst Close, Southgate, before he died aged 25 in 2011.
James, who fought cancer for 13 years, visited 92 football stadiums in 92 hours and raised nearly £7,000 for the charity a month before he passed away at its hospital in London.
Jo, who works with Ed, and James’s father, Nigel, at Tinsley House, a Gatwick immigration removal centre, said: “He held the hospital in such high regard I felt that’s the only way I could contribute and to remember James and what a wonderful person he was.
“For a Joe Bloggs like me, there’s nothing I can physically do other than raise some money to help the people that helped him.”
She added: “My dad had cancer and - touch wood - he survived. There’s all these charities and hospitals that do absolutely amazing work for dads and mums out there.”
The pair will start the walk on May 24.
Jo was walking about 40 miles per week in preparation for it. She had completed a four hour walk before she started work.
It will be the second time Jo will take on the walking challenge.
She completed the course and raised more than £4,000 for the RMH with Tony Stretch and Siobhan Franklin in 2012.
Jo said: “We made a grand total of £4,357.66, we were quite proud of ourselves.
“I said never again, it was just horrendous, but for some reason I had a weak moment in August last year.
“Ed, bless him, he’s a bit oblivious to it and thinks it’s going to be good fun - I’m thinking it’s going to be 30 hours of walking.
“Once I crossed finish line I never had the feeling of complete and utter achievement, I’ll think back to that.”
To sponsor Jo and Ed’s walk visit http://uk.virginmoneygiving.com/team/joandeds100kjourney