It's 7am on a Sunday morning and I've just run past the Tesco supermarket in Leighton Buzzard. Never before has running past a supermarket held so much significance for me. It was a year earlier that I had stopped here, exhausted and unable to continue. I knew those dreaded three letters, DNF (did not finish) next to my name in the results would haunt me until I returned to complete the race the next year. As I run through Leighton Buzzard I smile, remembering how much worse I felt last year, but also remembering there is still a long way to go if I’m to finish the race.

I've been running for more than 24 hours now, and I’ve completed 90 miles of Britain's longest and toughest non-stop race. I've got another 55 miles to go before I reach the finish of the 145 mile Grand Union Canal Race. The race starts from the centre of Birmingham and follows the Grand Union Canal all the way to the centre of London. Of the 70 competitors who started the race, only 27 will go on to cross the finish line in Little Venice, in times ranging from Matt Giles’ winning time of 29 hours 6 minutes to the official cut-off time of 45 hours.

I’ve already almost given up twice by this point. Just before the 70 mile checkpoint, I experienced a sharp pain in my ankle which stopped me in my tracks. Unable to walk, let alone run I resigned myself to retiring. I sat down to rest, and as my ankle began to swell up I decided to see if I could continue for a few miles. I soon got used to the pain.

This is a non-stop race; you are not allowed to stop for more than 40 minutes at a time so sleeping is not an option. As the hours pass by the tiredness sets in. By 80 miles I was so tired I began to fall asleep while running. Once again I almost gave up, I sat down for 10 minutes and shut my eyes, and when I opened them I once again felt ready to push on.

I have plenty of thinking time during the race. I remember how only five years ago I was dragged out of the house by my wife to struggle through my first one-mile training run, how I went on to complete my first five-mile race and six months later my first marathon. I remember the moment I crossed the line of the 2004 London to Brighton, knowing I could go further; that was the moment I had decided that I would attempt this race. Then I remember again how I failed last year.

The intense pain has been there for a long time now. The blisters cause the most pain, and I occasionally cry out as another one bursts. By now there is hardly any part of my feet that is not blistered. There is also the pain of my injured ankle and the general pain of tired muscles. It is almost unbearable, I know it will be there until the finish, but I also know it can’t get much worse.

The trick to a race like this is to remain positive and break the race down into manageable chunks. With 50 miles to go I try to focus on the next ten mile section. There are only another five ten mile sections ahead. The bad patches come more regularly now, but I remind myself how much I’ve already completed; I’m almost two thirds of the way through the race. I’ve hit “the wall” and got though it several times already and I know I’ll get through this bad patch and the many more that will follow.

It’s now been nine hours since I passed that Tesco supermarket. Ahead I see a flyover crossing the canal. It’s the M25 and I know London is getting closer. In another five miles I’ll only have a marathon distance to go. I’m starting to believe I can finish.

Five hours since passing under the M25 and I’ve now been running for more than 38 hours. As I make the turn to head north along the Paddington arm of the canal I know I’ve completed the equivalent of over five marathons and I only have a half marathon distance to complete. Until now I’ve not allowed myself to think of the distance left, but now I know I will finish and start to pick up the pace, picking off runners ahead one by one. Despite the intense pain and tiredness, I’m determined to enjoy this last section of the race. Forty two hours and six minutes after setting off from Birmingham, and this is the moment it has all been leading up to. I’ve been dreaming of crossing the finish line for the past year and with a few hundred metres to go the pain finally disappears and I begin to speed up. I feel like I’m sprinting as I approach the finish line. A small crowd cheers as I cross the line and finally I can sit down, knowing I’ve joined a very small and exclusive club of people who have completed Britain’s longest non-stop race.

It doesn’t matter if you’re finishing your first 5k race, a marathon or the Grand Union Canal Race - this is what it's all about, the feeling of satisfaction you get when you complete your goal, knowing you are ready to set yourself a new target. Five years ago I was thrilled to finish my first five mile race and now it’s time to find myself a new goal. What will you be doing in five years' time?