The bitterness has passed down through the centuries but Oliver Cromwell should no longer be allowed to affect relations between Britain and Ireland.
This viewpoint comes from Professor Colin Davis, a leading Cromwell expert at the University of East Anglia in Norwich, who believes he and fellow historians have a role to play to prevent people being prisoners of the past.
"When you look at Cromwell and Ireland, particularly after the New Model Army had taken Ireland, there is a really strong language being used about a clean sheet," said Prof Davis.
"One has to look for some sort of healing and a way of moving forward and I think that is where historians have a job to do. The danger is that we can allow ourselves to become prisoners of the past if we simply allow these old scores to determine what we do in the present.
"There is a real danger that Cromwell becomes a man for all seasons - that he is still a living presence. That cannot be right and that is where it is the historian's job to try and help.
He added: "From an English perspective the paradox is absolutely fascinating. He is the first to summon a British parliament. He is pulling Britain, for better or worse, together."
Historians have always held starkly differing views on Cromwell, who was born in Huntingdon, Cambridgeshire, on April 25, 1599. Some have viewed him as an enlightened figure who believed he was doing God's will. Others have classed him as an ambitious tyrant.
Cromwell was born into a wealthy landowning family but ranked near the bottom of the landowning elite.
For the first 40 years of his life he lived in relative obscurity and played no role in national politics.
He rose to power during the Civil War battles of the 1640s, joining the parliamentary army and revealing himself to be a brilliant military commander. As the Royalist army was defeated, he proved to be an accomplished military leader and statesman and became England's only Lord Protector in 1653.
He earned a monstrous reputation among Catholics after being sent to crush Irish rebellions in the late 1640s and early 1650s following the execution of King Charles I.
Following his death in 1658, the parliamentary cause fragmented and the monarchy was restored through the House of Stuart.
Prof Davis views Cromwell as a complex paradox who would remain one of the most famous figures in English history.
"I have been teaching history around the world for many years," he said. …