Possible wording - but suggest you modify to your personal wording:
“On Sunday 21st April I am running the London Marathon on behalf of Bedford Hospital Charity & Friends. I have always wanted to undertake this challenge and I will be taking part with a dozen other runners who are all running for BHC&F. Think of me whilst I am out on my training runs on cold winter nights around the town and you will understand that I need considerable motivation – not only with my training but also on the “big day”. Anything you can donate will be very much appreciated. Your sponsorship money will be going to provide much needed equipment at Bedford Hospital, and if you click on this link it will explain further:
https://www.peoplesfundraising.com/donation/BHCandF-Fundraising-Campaign
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