Stuart Mulrooney from Wesham has been overwhelmed with the response to his appeal for cash backing for his bid to run the 26 miles on Sunday, April 26 - without leaving his local area.
The idea started out as a way of keeping fit for the London Marathon's rearranged date in October when Stuart, 37, will be taking part in the event in aid of the Children With Cancer UK charity.
But within a couple of days of setting a target of £50 in aid of NHS charities for his local run on the original date, donations had soared above £300 and still climbing.
"It's wonderful - i'm overwhelmed with the response," said Stuart, who is JPI Media's North West regional sales manager.
"I was delighted to get into the London Marathon at the first attempt and started training seriously in January, covering more and more distance every day and it was going well.
"Along with so many other events, it has been postponed because of the coronavirus outbreak and I'm looking forward to taking part on the new date and raising lots of money for Children With Cancer UK.
"But seeing as I have trained my backside off for the past four months through numerous storms and miserable weather - including Storm Dennis on Blackpool prom - I thought I'd attempt to run one anyway and see if I can raise a small amount of money for the amazing doctors and nurses that are risking their lives everyday for us.
"I've worked out a route close to home which covers the same distance and the aim is to cover it at one go, with my partner Natalie Middlemas following in a back-up vehicle with water to keep me refreshed.
"This is nothing compared to what Captain Tom Moore has been doing at almost 100 years of age but it's extra money in the pot for the incredible NHS and I can put all the training to good use
"I'll be happy if I do it in around four hours and as well helping the NHS, it will be good practice for October.
"Everyone has been so generous and thanks so much for all the pledges."
Details of how to donate are at www.justgiving.com/fundraising/stu-mulrooney