The Duke of Cambridge will start the Ring O'Fire Anglesey Coastal Ultra Marathon on Anglesey later. The Ultra Marathon is an annual 135 mile coastal marathon circumnavigating the Isle of Anglesey. The foot race is staged over three days and follows the Anglesey Coastal Path around the island.
Prince William will meet a number of runners and their families and a selection of volunteers involved in the administration of the race before officially starting the Ultra Marathon.
The 135 mile distance and 13,695 feet of vertical ascent makes the Ring O' Fire one of the most extreme ultra marathons in the United Kingdom.
More top news
A milder feel than last night but there's wind and rain on the way, and ice will form in places too!
Public Health Wales has spoken to ITV Cymru Wales about how to safe and well during the winter months.
Paramedics are poised to deal with any emergency – but 35,000 feet in the air is the last place you'd expect to have to spring into action.