Blackwell is half way towards his donation target of £2,500.
The disclosed list of donors includes mortgage and industry luminaries John Malone of PMS, Eddie Goldsmith of Goldsmith Williams and e.surv’s Richard Sexton.
Blackwell said: “Joseph Foote is a charity close to my heart. The founders are close family friends who lost their little boy to a brain tumour when he was only nine. Only 15% of sufferers survive a brain tumour.
“The great work The Joseph Foote Trust is doing aims to propel that figure to 80% by 2022. Every little helps, and I want to do my part for a noble cause.”
Blackwell added that his wife told him the training would add years to his life.
He said: “I think she’s right, I feel ten years older already. And I keep getting asked whether my knee brace is a fancy dress item. Sadly it’s not, the guy dressed as Robocop has nothing to fear.
“It’s been over six years since I last ran the marathon, if the fridge and the TV weren’t so far apart I wouldn’t have had any exercise at all.
“I was aiming to start slowly then taper off but this time I’m aiming to shave 20 minutes off my personal best and trundle round in 4 hours 15 minutes.”
