This time last year Brian Thomas was recovering from critical injuries after collapsing while walking near his home in west Wales.
He was rushed to the Accident and Emergency unit at Withybush hospital who referred him immediately to University Hospital of Wales for brain surgery.
After spending four weeks in a coma, he was told by doctors that he would remain in hospital for more than a year and that it could take up to five years for him to fully recover from his injuries.
But, after eight weeks, to the shock of hospital staff, Captain Thomas was deemed well enough to be discharged. Now, through "sheer determination" and "family and friend support," he is hoping to complete today's Cardiff Half Marathon in two hours and 20 minutes.
During his stay in the Neurosurgical Unit, his surgeon John Martin gave him the catchphrase "Captain Thomas, the Captain that never sinks," which is fitting for Mr Thomas who was a sea captain on Queen Elizabeth 2.
Captain Thomas is raising money for the A & E unit of Withybush Hospital and so far has raised more than a thousand pounds.
Thousands of people, like Brian Thomas, will be running in Sunday's marathon which starts at 9am.
Many will do so in memory of a loved one such as Karen and Graham Morgan whose daughter Kate died of meningitis earlier this year. Kate, who was 18-years-old and from Cardiff, was described by her family as a "beautiful, inspirational girl with a fun-loving nature".
A team of around 20 people, including her parents and brother Ben, will take part in the marathon to raise money for Meningitis UK.
Last year's Cardiff Half-Marathon was a sell-out with a record number of runners, more than 15,000 people, taking part.