Hawksmoor By Peter Ackroyd

There is no Light without Darknesse and no Substance without Shaddowe'
So proclaims Nicholas Dyer, assistant to Sir Christopher Wren and man with a commission to build seven London churches to stand as beacons of the enlightenment. But Dyer plans to conceal a dark secret at the heart of each church - to create a forbidding architecture that will survive for eternity. 
Two hundred and fifty years later, London detective Nicholas Hawksmoor is investigating a series of gruesome murders on the sites of certain eighteenth-century churches - crimes that make no sense to the modern mind ...