The Duke of Cambridge is making one of his final public engagements on Anglesey as the new father's time on the island comes to an end.
William will be joined by Kate as he starts the gruelling, three-day annual "ultra" marathon run around the coast of the island, known as the Ring O' Fire.
The Duke and Duchess will meet some of the runners and their families and volunteers before the start - but the couple will not be bringing the royal baby.
The annual event is a 135-mile foot race around the rugged coast of Anglesey, staged over three days and including 13,695 feet of ascent.
The last time the Duchess was seen in public was the day after the birth of Prince George.
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The day will get off to a bright but chilly start, with a few mist patches in rural areas. Showers will spread inland throughout the day.