Oliver is quite well regarded in this area, which was a Parliamentarian stronghold. There's a big statue of him in front of the Warrington Guardian office in the town centre and, next door to Sainsburys, there's an old timber framed cottage that used to be called "Cromwell's cottage" but is now just "The Cottage" - since it became an Indian restaurant. He's supposed to have stayed there for a while. Presumably he wsn't eating curries at the time.
Saint or sinner? I think he sincerely believed in his cause and there was some justification in deposing the king (killing him, however, was an unjustifiable fit of pique). I think the era of puritanism Cromwell brought in was stifling and, if I'd been around then, I'd have been glad to see Charles II bring a bit of bawdiness back......but, then, that's just me!
