From 1638, when this story starts, to its end twenty years later, Oliver Cromwell went on a roller-coaster ride through English history. Historians have argued about him and his motives ever since, but no-one's been able to hear it from his point of view - until now. In chewing over events with his cat, Tomkins, Cromwell at last tells it like it was. 
After all, when did your cat ever ask you "Who are you trying to impress?" Never, of course – and neither does Tomkins. He hears all and, because he and Cromwell find early on that they talk the same language, he reveals all: Cromwell's take on the Putney debates, the trial and Execution of Charles 1; his installation as Lord Protector and many more.
So, the obscure-ish Ely gentleman, who by virtue of his military achievements rose to be almost but not quite King, finally gets to speak uncensored. And because the language barrier once-breached, becomes infinitely breachable, readers find they can ask him questions for which no-one hitherto (not teachers, not examiners, not historians and certainly not politicians) has ever known the answer. He tells of his belief that God was driving the rollercoaster – buoying him up on the highs (when Christ's second coming and the rule of the saints seemed at hand) – and driving him on through the lows (and there were many) when he realised he'd got it wrong and the Lord must have been looking for something different.
Losing friends, finding enemies but never losing hope, convinced throughout that the Lord had a special providence for England - and for him.