The English Monster, By Lloyd Shepherd

The waterman constable and the bogeyman

Non-spoiler alert! There is a dark twist – a spot of black-magical realism, if you like – about halfway through Lloyd Shepherd's first novel that this reviewer has no desire to ruin for readers. In fact, so delicious and unexpected is this turn of events that it moves a book that is already part detective fiction, part historical novel and part pirate adventure into entirely new territory, adding themes of natural philosophy and moral turpitude to a story as rich in ideas as it is in intrigue.

To the plot then. Or to be precise, the plots. The first (chronologically, at least) concerns a young man named Billy Ablass who, in 1564, heads to Plymouth to seek his fortune at sea. Taken on by one John Hawkyns, Ablass soon discovers that not everything on board the Jesus of Lubeck is, well, above board.

As that story sets itself in choppy motion, chapters alternate between Ablass's mission and the Ratcliffe Highway murders so dutifully described in P D James and T A Critchley's 1971 true-crime book The Maul and the Pear Tree. The gruesome murder, in 1811, of Timothy Marr and his young family is replayed again here in graphic detail. Though the Age of Reason has America in its grip, policing in Britain is still a bewildering arrangement between local magistrates, parish watchmen and – in the newly thriving docklands of London's East End – waterman-constables.

Charles Horton is one of the latter, the eyes and ears of John Harriott, immortalised on his memorial stone as "progenitor of the Thames Police". Horton is a man with new ideas: Harriott can find only the words "detection" and "investigation" to describe what it is that Horton does. As the everyman cop applies such techniques to the Ratcliffe Highway murders, he pieces together a theory that will pit him against the Shadwell magistrates whose job it is to serve the guilty party up to the ravenous public.

So, what could possibly tie Britain's first authorised slave ship to a series of shocking murders some 250 years later? My lips are sealed. Soon, the Shadwell magistrates arrest and charge the hapless Irish itinerant John Williams, and Shepherd's analysis of the past is perceptive enough to draw parallels with current events (say, the Leveson inquiry): "Everyone felt that London's panic and fright had changed register, and had turned into a type of fascination. Here's the likely culprit, said the newspapers and magistrates. We've got him. Sleep easier in your beds. The bogey-man is under lock and key."

If all this sounds ambitious to the point of audacious for a debut novel, then suffice it to say that Shepherd pulls it off. Add (mostly) accurate biographical details from the lives of Francis Drake, Hans Sloane, Henry Morgan and Aaron Graham to a story already centred around the real-life characters of Harriott, Horton and Hawkyns, and The English Monster becomes as vivid an education as it is an entertainment. None of which is to mention that devilish twist in this tale.