Louis Ashbourne Serkis
Alexander "Alex" Elliot
Dean Chaumoo
Bedders
Tom Taylor
Lance
Rhianna Dorris
Kaye
Denise Gough
Mrs. Elliot
Angus Imrie
Merlin
Patrick Stewart
Old Merlin
Rebecca Ferguson
Morgana
Genevieve O'Reilly
Sophie
Noma Dumezweni
Mrs. Lee
Nathan Stewart-Jarrett
Mr. Kepler
Mark Bonnar
Mr. Jeffreys
Alexandra Roach
Ms. Foster
Nick Mohammed
Mr. Hyde
Adam Buxton
Stonehenge Tour Guide
Claudie Blakley
Riding Instructor
Myra McFadyen
Punto Patty
Adam Leese
Policeman
Joey Ansah
Policeman
Amir Wilson
Boy (uncredited)