Scott Thornton, from Glasgow's Merchant City, will pound the streets in this year's London Marathon to help Enable Scotland.
The charity, is close to his heart because one of his daughters, Fiona, 27, has learning difficulties and is profoundly deaf.
The father of three, who owns Hotel PR, a specialist public relations company, said: "Through my daughter I have come into contact with lots of people who have learning difficulties and I think they get a raw deal.
"I don't think they get nearly as much funding as they should, so Enable is my choice of charity.
"Besides, it is also a Scottish charity and I wanted to support a Scottish charity."
His oldest daughter, Laura, 34, is a fundraising manager with Macmillan Cancer Care.
Mr Thornton said watching her run the London Marathon for charity in 2006 and 2008 inspired him to give it a go.
He said: "I was very proud of her and I thought, before I got too decrepit, I would give it a try."
Although he only began running in September 2010, Mr Thornton has been training hard and is determined to complete the 26-mile challenge, which is on April 22.
He runs two to three times a week, enjoying routes around Glasgow Green and along the Clyde, as well as going to the Gorbals Leisure Centre gym.
He has already run three half marathons, including last year's Great Scottish Run, but he said he was "nervous" about the marathon.
Granddaughter, Isla – Laura's daughter – will be on the sidelines cheering him on. Mr Thornton, formerly a foreign correspondent with Reuters news agency, came to Glasgow four years ago with wife Julia, 61.
He also has a 17-year-old son, Andrew.