For the English ( not the Scots), emotions are a bit lower, though even there in 2000, the anniversary of Cromwell’s return from Ireland, the historian and leading Cromwell authority Professor John Murrill suffered for his interest in Cromwell: 

“I was myself assaulted and received death threats. The depth of
hatred that still exists in Ireland is matched only by unawareness in non-Catholic
English circles of what Cromwell did in Ireland. I am reminded of GK Chesterton’s
remark that the tragedy of the English conquest of Ireland in the 17th century is
that the Irish can never forget it and the English can never remember it.”

Might the reason for all this unpleasantness have something to do with the fact that good professor was President of the Cromwell Association, and may be supposed to have plenty of good words to say on old Ironside’s behalf?  Was he therefore the right man to be reviewing Cromwell’s life and work in BBC History magazine?.  On inquiry, that seems unfair to him.  A summary of the prof’s views suggests a more dispassionate view than the Irish, but very far from a whitewash. This for instance on the Siege of Drogheda which ended with the massacre after surrender of 2,500 immediately and hundreds more later.

“It was in accordance with the laws of war, but it went far beyond what any General had done in England. Cromwell then perpetrated a messier massacre at Wexford. Thereafter most towns surrendered on his approach, and he scrupulously observed surrender articles and spared the lives of soldiers and civilians. It was and is a controversial conquest. But, from the English point of view, it worked’

On the same occasion, Morrill, who is Professor of British and Irish History at the University of Cambridge contributed an article entitled ‘Was Cromwell a War Criminal?’
This is a carefully balanced piece “ for” and “against” but “against” contains the conclusion:

“This was ethnic cleansing on a scale undreamt of by Slobodan Milosevic”

I’ve always thought of Cromwell as follows. In the tsunami of religious conflict compared to our own pond ripples that was the 17th century, Cromwell was the epitome of the disciplined fanatic, who became an outstanding military leader out of his status and ability to raise a regiment in Huntingdonshire. He achieved this by the then revolutionary method of showing his fellow men respect as fellow Christians, training them – and paying them. None of that feudal nonsense any more.  Decidedly less favourably, as a Bible Protestant who nonetheless tolerated other Protestants in an intolerant age, he despised the Catholic Irish - and Catholic English - as being beyond the Pale ( even if they were in it if you see what I mean).

At Drogheda he employed usual siege warfare conventions. In those days,besiegers were almost as vulnerable as the besieged because of exposed supply lines and an ever-present threat of disease. So the besiegers warned those cooped up that if they didn’t surrender by XX, they’d be massacred. Which they duly were. And most of them were English. But although Cromwell must be judged mainly by the standards of his time. I’m now convinced he brought an extra edge to the business.

As O’Toole puts it: ( His conduct at Drogheda was) a refusal to distinguish between civilians and combatants and a resort to ethnic cleansing. In his first engagement, at Drogheda, he personally supervised the slaughter of about 2,500 soldiers and an indeterminate number of civilians. The arguments of apologists that this was within the laws of war at the time are contradicted by the evidence in Cromwell’s own account that he himself understood the scale of the massacre to be exceptional. It would, he admitted, have prompted ‘remorse and regret’ were it not intended to have exemplary effect as both collective punishment and a warning for the future.”

In England I see Cromwell as a sort of latter day Musharriff, executing the previous leader, always dissolving parliaments, shooting democrats ( the Levellers at Burford Church) and claiming divine inspiration for the lot. And… so totally failing to create a stable regime that they had to bring back the old one. The TV historian Tristram Hunt likens him to a puritanical ruthless Taliban leader.

Yet you can’t eliminate him from the history of the British constitution, as the unifier of the three kingdoms who still leaves trace elements behind in the DNA of the development of British democracy, even up to today.

Hunt states:
“Reverence for Cromwell was one of the few socialist traditions that survived the transition from old to new Labour. Frank Dobson, a politician whose career symbolises the difficulty of that passage, is a leading light (along with Lady Antonia Fraser) of the Cromwell Association. And Dobson shares the same machine-politics admiration for the Roundheads that Tawney expressed. “For me, it boils down to this,” he responded to a question about Cromwell’s actions at Drogheda. “He was on the right side in the civil war and, because of him, the right side won. He changed the course of English history, and changed it for the better.”

But I found quite the best romantic English revolutionary view of Cromwell in a Communist site – appropriately enough - for I was taught Cromwell by the historian they revere, the very late revisionist Christopher Hill. Cromwell swept away the feudal order, and installed the bourgeoisie in the second stage of the English Revolution. That’s why he remains something of an English hero to the English broad left.

We’re still waiting for the third stage.

P.S. Should you be concerned - yes Cromwell’s Irish record is exposed in the English national curriculum.