When Dennis comes into possession of a book that shouldn't exist, a new chapter in his life begins and a different, alternate London reveals itself - and with it a cast of characters each more unlikely and fantastical than the last. Long London occupies precisely the same geographical space as our London ­- but it is a city built from dreamscapes and art, from fiction and nightmares.

This is the London of penny dreadfuls and William Blake's dark woodcuts, colliding with Dennis' ow...