Prince William, Duke of Cambridge with Prince George and Princess Charlotte at the start of the half marathon on the Sandringham Estate. Picture: Ian Burt

Surprised runners were given a royal countdown when they lined up for a new event yesterday (Sunday).

The Duke of Cambridge and his two eldest children Prince George, 7, and Princess Charlotte, 6, started the half-marathon runners off at the Run Sandringham event held on the royal estate. 

Prince William, who celebrates his 39th birthday today (Monday), spent part of his Father’s Day supporting the participants.

Race director Aaron Murrell said the runners enjoyed seeing the Duke and family, who live at nearby Anmer.

An estimated 1,300 runners took part in the new event which also included a 5k and a community mile for all ages and abilities.

A number of charities benefitted from the Good Running Events day, including the organisers’ choices of the East Anglian Air Ambulance, Break and East Anglia’s Children’s Hospices with runners also supporting their own causes. 

After the event, Sandringham Estate took to social media and tweeted said it was “sterling stuff from all the runners… despite the damp weather.”

Another event is planned around the estate on Sunday, September  26 which will be a fundraising 10k.