St John writes with apparent ease, but refuses to compromise on language while mixing modern life (Kat has a mobile phone by her bed — I’m not sure Matt Hancock would approve — and Harper is admirably tech-savvy) with old-fashioned Blyton-style follow-the-clues mystery. It’s an excellent combo. If this first invigorating book is anything to go by, St John had better start writing some follow-ups.
St John is a wonderful writer, who lets the adventure hurtle without ever making the reader feel hurried. Mysteries thicken, lives are at stake – but when it comes to a picnic, no ingredient is forgotten: "There [was] a salad and chocolate cake freshly baked scones, jam and clotted cream, and Dr Wolfe was stopping en route to pick up chips, dips and ginger beer." This is just the sort of thoroughly wholesome novel that should really be consumed outdoors.