100 ultramarathons in 100 days: former rugby pro hit by brain injury nears end of feat

David 'Jacko' Jackson has not shaved during his challenge – his beard is ‘almost a symbol of how far I’ve run’, he says. Photograph: Francesca Jones/The Guardian

The key for David “Jacko” Jackson is to take each stage nice and gently. “It’s not about running fast,” he said. “It’s more like the hare and tortoise story. Slow and steady – and do it again tomorrow.”

So far, so good. Jackson, a former professional rugby player who retired after a traumatic brain injury, is nearing the end of an extraordinary bid to run 100 ultramarathons (50km, or about 30 miles) in 100 consecutive days.