The actor, who played 'Nasty' Nick Cotton on U.K. soap Eastenders has signed on to play Earl Leofric of Mercia in 1066.
Announcing the news of his latest casting coup, director Robin Jacob tells WENN, "We are very pleased to announce John's involvement in 1066. He is a great actor who will bring his wealth of experience to the set."
His new film character, Earl Leofric, was one of the most powerful members of the council of Anglo Saxon Earls, clergy and nobles known as the Witan.
Former child star Lester was one of the first people cast in the film - he will portray King Henry II. The movie will also feature Susan George, Lewis Collins and Finding Neverland actress Kate Maberly.