21-year-old actor Ed McVey was spotted wearing tracksuit bottoms and a hoodie with the University of St Andrews logo on it while being filmed running at the town’s East Scores.
Sightings of Dominic West, 53, who is playing William’s father Charles, and Meg Bellamy, 19, who is playing the Princess of Wales, have previously been reported in the town.
In the series, Elizabeth Debicki will reprise her role as William’s mother Diana, with Imelda Staunton continuing as the Queen and Jonathan Pryce as the Duke of Edinburgh.
The last series chronicled the divorce of Charles and Diana.
It was due to end after the fifth series, but the show’s creator and writer Peter Morgan later said it would be extended to a sixth.
In the series, Elizabeth Debicki will reprise her role as William’s mother Diana, with Imelda Staunton continuing as the Queen and Jonathan Pryce as the Duke of Edinburgh.