In the new film The Eagle, based upon Rosemary Sutcliff‘s The Eagle of the Ninth – historical novel for children,  young adults and indeed adults – Director Kevin McDonald:

… does an amazing job of recreating Roman life in lower Brittany, staging battles and creating a tribe of “Seal people” with a budget somewhere south of $25 million. According to Richard Billows, a professor of Roman history at Columbia University, who attended the film with us, about the only thing McDonald got seriously wrong was a brief moment in a battle scene where Marcus instructs his men to retreat in the face of a charging chariot…Centurions were trained to form a wall and stand their ground, thereby forcing the horse to stop in its tracks.
Source: Review: “The Eagle” Soars | NBC Connecticut.

• More on the film, movie The Eagle from The Eagle of the Ninth on this blog