This is an interesting book all about the goings on underneath London, delving into archeology, underground rivers, the Tube, sewers and all kinds of other subterranean bits and pieces. I remember hearing rumours (and probably spreading them too) of there being various secret tunnels connecting government buildings and other institutions when I was a student in London and this would have been great to read then (long before it was published however) which was why I snapped it up to read when I saw it in the bookshop. It took me ages to read it because every chapter sent me off to commune with a search engine and find out more using the things Ackroyd had just informed me about as the start of a search. Ultimately that’s my only disappointment with the book - it’s brief and a jumping off point for doing your own research, not a fully researched historical volume in itself.