Former rugby player to finish 100 ultramarathons in 100 days at Caernarfon Castle

David "Jacko" Jackson, 44, is set to finish 100 ultramarathons — each roughly 30 miles — in 100 consecutive days at Caernarfon Castle on 5 September. A traumatic brain injury ended his rugby career in 2013. He is raising funds for Headway and Head for Change. Over 700 people ran alongside him en route.