Dale Lyons, aged 81, is one of just 11 "ever presents" - the dwindling band of men who have crossed the finish line at every marathon since the first was held in 1981.
Last year, he completed the course in six hours, 23 minutes and will be pounding the streets of the capital for the 38th time today - although the father-of-two will have to do the route on crutches, as he continues to struggle with sciatica and a number of injuries.
This year he will be raising money for the national disability charity Sense and has set himself the target of finishing the 26.2mile route in under eight hours.
To find out more about the "ever present" runners, visit their website
- The "ever presents" were first recognised in 1995 - the year of the 15th London Marathon. Even back then there were only 42 runners who had completed every race, with the club reduced to 11 at last year's event.
- Four years ago, Dale released a book - The Real London Marathon Men - charting the group's endeavours.
- Dale has notched up a number of achievements over the decades and previously broke the Guinness World Record for fastest marathon tossing a pancake.