Critical reception was positive, though there was some criticism of the omission of some figures and events (such as John Pym, the Earl of Bedford, Sir Thomas Fairfax, Sir Denzil Holles, 1st Baron Holles, Edward Hyde, 1st Earl of Clarendon, Colonel Sir John Hutchinson, Henry Ireton and the Bishops' Wars) and the fictionalisation of others (such as the suggestion that Cromwell orchestrated Rainsborough's death,[4] of Rainsborough not Sexby being a close friend of Cromwell's, Sexby's going to Ireland and the losing of his arm and Sexby's assassination attempt on Cromwell[5]).

Critical reception of the first episode was positive, with Nancy Banks-Smith of The Guardian praising Capaldi's performance and calling the drama "rollicking", "well written and acted" and marked by "a quite serious attempt to explain the underlying issues".

[8] The Times called it "a curious beast – mannered and theatrical, with modern-looking faces speaking period dialogue in an historical dreamscape" and "If not entirely successful, ... the best sort of failure – unusual, brave and fascinating".

[9] Another Times critic criticised it for "slightly too much reading history backwards here, almost making Angelica look like a modern woman travelled back in time" and its "frankly unnecessary bedroom scenes ... slipped in, presumably to demonstrate her liberated nature", whilst overall praising the episode as "gripping", "cutting" and "lively" and in particular noting that Simm played Sexby "strikingly".

[11] John Adamson, a non-stipendiary by-fellow in History at Peterhouse, Cambridge, criticized the series as "a cartoon-strip version of the Civil War".