The City of Guardian Stones (City of Secret Rivers)

Hyacinth has just saved London, and possibly the world, from a magical conspiracy stretching back centuries. Not bad for a week of summer holiday. But why is her family linked to the ancient secrets of London? Hyacinth needs to find out, and when she discovers that Ancient Roman stones are being stolen from all around the city, it's time for another adventure with the help of friends new and old, including Oaroboarus, a giant pig in a swimsuit.

A fast-paced caper with a magical cast of characters including the dastardly Minnie Tickle whose skin is inscribed with powerful tattooes, a host of opinionated living stone sculptures, Hyacinth's new neighbour Dasra (who may or may not be trustworthy) and the Corkers: a police force made entirely out of cork.