Trivia

When writer / director Ken Hughes said to Richard Harris that no self-respecting Irishman should ever play Oliver Cromwell, Harris laughed.

Due to "The Troubles" in Northern Ireland, scenes showing Cromwell's campaign in Ireland were cut.

Close to 4000 costumes were made, 16,000 separate prop items found or made, and thousands of wigs ordered from all over Europe.

Most of the film was shot in England, and London's Parliament Square was constructed at Shepperton Studios, but the battle scenes were shot in Spain. The original cut went for three hours 15 minutes but Hughes cut it down to two hours twenty four minutes. "I think it's the best thing I've ever done," said Hughes in 1970.

More than 200 workers at Shepperton Studios built the largest outdoor set ever constructed for an English-made movie, a two-acre re-creation of London's Parliament Square as it looked in 1642, complete with the House of Commons, Westminster Palace and Abbey, and roughly 50 other buildings.

Richard Harris was perhaps the least likely candidate for the role of the Puritan leader who, according to many historians, carried out near genocide in Ireland. Although a fierce Irish nationalist, Harris saw past the historical circumstances and became intrigued with Cromwell as "a symbol of integrity, anxious to reform society." Harris insisted it wasn't necessary for an actor to strictly believe in the character he was playing. Instead, he drew inspiration from Cromwell's idealistic nature, his goal to take the country out of aristocratic hands, and his "rigorous self-discipline", a trait Harris admired. More modern historians have questioned the view that Cromwell carried out genocide or near-genocide in Ireland, pointing out that the worst atrocities took place under the direction of other generals after he had returned to England.