Keen walker Mr Moffatt, 54, is raising money for the Devon Air Ambulance and Clic (Cancer and Leukaemia in Childhood) by walking from John O'Groats to Land's End. The 45-day expedition starts on Saturday, April 24.
Mr Moffatt, from Holcombe, near Dawlish, said: "It's going to be tough, but I'm looking forward to the challenge and, hopefully, a sizeable sum can be collected for the charities.
"I will be doing it completely alone - without any back-up or support vehicle - and aim to stay in guest houses and youth hostels along the way."
Mr Moffatt selected the charities after hearing that the Devon Air Ambulance was struggling for cash and chose Clic in memory of his father, who died from cancer. He is paying his own overheads and that all the cash raised will go to charity.
For sponsorship details contact Mr Moffatt on 01626 863622.