Stuck in 17th century England, the Doctor's delight in mischievous exploration results in Ben being stranded in Amsterdam, Polly lost and alone in London, and himself and Jamie captives of Oliver Cromwell, trying hard not to let his clumsiness affect the outcome of the Civil Wars.

An admission: as a Scottish republican with little interest in history and even less in the ups and downs of the English monarchy, I might have anticipated problems with this book. However, since even now I couldn't say who is historical and who is fictional - apart from the famous ones - I couldn't predict events, having no idea whose fate was pre-ordained by recorded history.

A story very much in the serious, educational style of the early Hartnell historicals, any similarities The Roundheads has to The Highlanders are probably due to sharing a regular cast and being not too far removed in time and location. It's more intelligent than the average Troughton story, and has pleasing portrayals of Ben and Polly, the only second Doctor companions I have time for. The Doctor is accurate - I fail to see what is reportedly so difficult about capturing this character; his childishness and intermittent inexplicable stupidity are precise. A typical lack of consideration for the implications of his actions almost has serious repercussions. Having foolishly brought with him a highly anachronistic 20th century book, the Doctor encounters problems obvious enough for the reader to predict.

His other inadequately explained decision at the start of the book, that the crew should split up, seems a Nationesque plot device to kick-start the story, and leave them spending the remainder of the book trying to get out of the hideous mess the Doctor has unapologetically left them in. Anyone who has seen The Tomb of the Cybermen and wondered about motives for opening the tombs will recognise this Doctor, who is paradoxically more likeable in print, lacking the affectations of the TV version.

Keeping track of the beliefs of each supporting character is not easy. In this context that is fine, since it is emphasised that this was a period of history with loyalties in flux. It would be foolish to expect an obviously complex political situation to be depicted any other way. Sal Winter, the startlingly athletic one-legged captain of the Demeter who encounters Ben in Amsterdam, is easily distinguishable. She does, of course, have a peg-leg and an artificial nose (quality metal, no rivets).

A complaint: why the intermittent phonetic reporting of Jamie McCrimmon's speech? If this must be done (and I don't see why, you don't catch Scottish writers missing out Rs and flattening vowels in reference to BBC English), some consistency would be nice.

In summary: considerable improvement for Mark Gatiss after the later, disappointing, PROBE videos. Will we see more, now that Perrier award-winning comedy beckons?