Derek Adams, 81, is aiming to complete the trek before he reaches 85.
He has already walked about 2,400 miles and, apart from being a great adventure, it's also in the cause of raising money for three charities, namely the RNLI (a lifeboat charity), Cancer Research UK, and the British Heart Foundation.
"I do have a wanderlust, but it's meeting people that's important," he told BBC News. "Maps are fine - and I love maps - but the best thing is asking local people." Starting in June 2022, Mr Adams has already trekked up the east coast of England and Scotland, as well around the south and west of England. His said his walk around Wales earlier this year had been the highlight so far.
The next part of his journey will cover Merseyside - before he heads up to Blackpool and onto Scotland. Being an octogenarian, he's wisely undertaking his UK walking odyssey in intermittent chunks, rather than non-stop. He's also being supported by Travelodge, a chain of budget-priced hotels, so he can sleep comfortably at night a discounted rate.
Mr Adams said he felt "superb" and "on top of the world" ahead of his latest stint, and thanked his "smashing family" and "wonderful wife" for their support.
When asked how he found the navigation, he joked: "As long as I keep the sea on my left, I know I'm going in the right direction."
If you would like to make a charitable donation to help keep him motivated, go to JustGiving