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)

Sean Coleman

Student Fighter