The best books about secret subterranean London

I wrote a novel, a thriller set in and around Westminster, a place I know well because I was a senior civil servant in Whitehall for many years. This included a number of little-known and ancient subterranean locations, including Roman baths, plague pits, the sewers, the Underground, the 'lost' River Tyburn, and World War Two bunkers. The Subterranean Guide filled in the blanks in my knowledge and opened up other aspects of this hidden world to me. It's a treasure trove of information and written with a light touch that engages everyone from the casual reader to the history geeks like me.

I have always admired the pioneering Victorian engineers like Stephenson and Brunel, but especially Sir Joseph Bazalgette, who is less recognised and honoured than others, but whose genius provided a sewage system for London which improved sanitation, reduced disease, and death, allowed for the development of the Embankment and lasted for over a century! This book tells the story of those sewers and ones like them across the world and the remarkable men who designed and built them, many of them little known to their countrymen and women. It's absolutely fascinating, from the technical details to the social impact. It has turned me into a sewer aficionado.

I enjoy Ackroyd's novels as well as his biographies, the former almost always being set in London which he, as a noted flaneur, loves. London Under is not fiction, though it often references the literature and mythologies which have grown up around certain places and landmarks within London, from its earliest incarnation before it was even a city to the present day. Ackroyd chronicles how the London of one time reappears and impacts upon the London of another time, one stratum intruding upon another and shows how the world below mirrors and reflects the world above. This is not unlike how I wanted the clandestine and criminal world to mirror and reflect the above ground and above-board world in my novel Plague.

OK, this isn't focused on the subterranean, but it does touch frequently upon underpasses and tunnels and is a personal journey, passing through the parts of London where the 'Ginger Line' - the London Overground railway -  runs. Sinclair uses his experiences to illuminate the changing city, a jumping-off point for explorations of places, their past, and present. His journey is bound up with writers and artists of all kinds. He, like Ackroyd, has an eye for the bizarre, but Sinclair has a sense of danger, real and modern, while Ackroyd summons the haunting past.

The System is the third book in the Baroque Cycle which begins with Quicksilver and continues with The Confusion. The whole Cycle is a rip-roaring, wildly inventive, and massively ambitious saga, ranging from the mid-seventeenth to the early eighteenth century, spanning the globe and casting an amazing set of characters from Leibnitz and Newton, to King George, Thomas Newcomen and William Teach the pirate. It's astonishing and has some of the best subterranean London episodes I've ever read, including an escape from Newgate Prison which takes in the Bank of England, a Roman Temple, and a medieval privy. Read all three books and hang on to your hats, it's a thrilling ride.