I'll be running the 26 miles and 385 yards on April 13 (9 weeks next Sunday) for NCH, the children's charity.
I'm normally sceptical about hacks who make fools of themselves for "char-i-dee" but fatherhood has changed my perspective on life in many ways.
NCH help some of the most vulnerable children in the UK. They make families happen for children who would otherwise be in care, helping to give them a better start in life.
I should, as they say, declare an interest. NCH played a key role in bringing our family together - that's one reason why I've chosen to run for them.
Before you rush to post your cheque, let me alert you to an easier way of giving - justgiving.com/davidcornock. The site explains more about NCH and what they do.
You can also donate by cash or cheque - or even via a think tank of your choice. You can claim tax relief on donations - and you don't need to declare it in the register of interests.
All contributions, however small, gratefully received. It's a very good cause - and you get the bonus that I'll be gaining sore legs, blistered feet and aching muscles in the process.
The marathon may be two months away but please give now before you forget. It'll save you a knock on the door from my heavies in April. Remember, I know where you live....(well the IP address anyway).