•
Freddie Highmore as Justin, a teenage boy who dreams of becoming a knight like his grandfather before him. Justin soon sets out on a quest to achieve his dream. He is shy, lacks confidence, has a slight build, and is clumsy, but is also brave, determined, true of heart, smart, and rather handsome. •
Saoirse Ronan as Talia, a teenage girl and former barmaid who comes from a large family of many older brothers. Tired of her job and seeking the thrill of adventure Talia joins Justin, eventually becoming her best friend and falling deeply in love with him. She is beautiful with long brown hair, is skilled at fighting, is quick-witted, loves adventure, and cares for others greatly. •
James Cosmo as Blucher, one of the monks, a former knight and Sir Roland's best friend. •
Charles Dance as Legantir, the wise head monk and wizard. •
Tamsin Egerton as Lara, Justin's former crush and the daughter of the kingdom's pioneer economic. She has blonde hair, has many dresses and makeup, and is rather selfish and insensitive to others' feelings. •
Antonio Banderas as Clorex, an armour polisher and thief who poses as a knight for fame and money. •
Rupert Everett as Sota, a vain but skilled swordsman who serves Heraclio as his right-hand man. He has two brothers he bullies constantly. •
Barry Humphries as Braulio, a monk and inventor. He suffers from a nervous condition that causes seizures when stressed or upset, especially during Justin's training. •
Alfred Molina as Reginald, Justin's father. He is the chief lawyer of the kingdom and vehemently against knights. He wishes for his son to become a lawyer like him. •
Mark Strong as Heraclio, a former knight who betrayed his kingdom and murdered Sir Roland. He blames the Queen and Reginald for ruining his life by outlawing knights. •
David Walliams as Melquiades / Karolius, a quirky wizard with a bizarre split personality that prevents him from using magic as neither personality likes the other or can agree on anything. Both personalities accompany Justin and Talia on their travels as it is the one thing they agree on. •
Julie Walters as Grandma Lilly, Justin's grandmother and Reginald's mother. She supports Justin in his desire to be a knight and strongly disagrees with Reginald outlawing knights. She is good friends with the Queen. •
Olivia Williams as the Queen of Gabylonia, the governor of the kingdom. Following her husband's murder, she outlawed all knights, hoping to prevent any future conflict, but now realizes her actions have left her kingdom and people with none to defend them. •
Richard O'Brien as Innkeeper of the Broken Eagle Inn, an angry businessman who only cares about money. He allows his guards, Igor and Slamski, to bully Talia and customers alike. He is the main cause of Talia quitting her job to adventure with Justin. • Lloyd Hutchinson as Champ, Sota's giant brother who bears most of Sota's bullying due to his low intelligence. He switches sides and aids Justin and Talia after Justin treats him with kindness. Hutchinson also voices Igor, a guard at the Broken Eagle Inn. • Stephen Hughes as Copas, Sota's cheerfully drunk brother who owns a horse, Skipper, that thinks it is a dog. • Matt Wilkinson as Slamski, Igor's twin brother, another guard at the Broken Eagle Inn. •
Michael Culkin as Sebastien, Lara's butler. ==Reception==