Holly, and her best pal Jessica Chapman were killed by school caretaker Ian Huntley 10 years ago, after leaving Holly's house following a family barbecue.
The little girls were just 10 years old, and their bodies were not found for nearly a fortnight after their disappearance. Huntley is serving a life sentence for their murder.
Kevin Wells became the founding patron for the Grief Encounter charity, and has chosen to run this year's marathon to support them.
He told the Cambridge News: "We have met some extraordinary people through Grief Encounter since we became involved. There are some awful cases that the counsellors have worked with, heart-rending stuff, and the charity's services are oversubscribed. I want to do more to help if I can."
Holly would have turned 21 this year, and her dad said it was good to do something 'positive' to mark the 10 year anniversary of her death:
"Not only is this year the 10th anniversary of Holly, it's also Olympic year, and I realised it was a great opportunity to trumpet the charity, as well as do something positive to mark the anniversary," he said.
In the interview, Mr Wells said he did not want to talk about the past 10 years, and how Holly's murder affected his family but simply to focus on the run and charity, saying the organisation provided 'the kind of help we all hope that we'll never need to consider'. He said he was "genuinely overwhelmed when my wife and I found out a charity like Grief Encounter existed."
He said the grief handbook given to him by the charity have him 'permission to grieve for Holly for the rest of my life. I'm now proud to help this charity.'
Mr Wells said that between him and his running partner Rob Wright he hoped to raise £10,000.
They have set up a fund-raising page at www.justgiving.com/kevin-wells
We wish Kevin Wells lots of luck with his run.