The Lady in the Moon Moth Mask, the forthcoming book in The Secret of the Tirthas, takes place in a fabulous country house based on Polesden Lacey, a property near Dorking that was almost bequeathed to the Queen but ended up in the hands of the National Trust.

My wife and I take our boys there on a regular basis, as they love amongst other things getting their hands on old stuff, grandfather clocks, the chickens when they’re not away on holidays, and, appropriately, the stone griffins. Plus the grounds are huge, and beautiful, so there’s plenty of space to run around.

I always wanted the series to be very diverse, with equal parts mystery and action, and a strong contrast between the exotic and well-known. After Lizzie’s harrowing ordeal in the Cameroonian jungle in The Dreamer Falls, I decided to revert to a gentler setting, with the emphasis once again on mystery and intriguing characters.

After watching an excellent BBC adaptation of Agatha Christie’s And Then There Were None (and then reading the no-less-brilliant book) I knew Lizzie’s story leant itself to the same kind of set-up. So I did some research and took a lot of photos of the building, uncovering more of the absorbing story of Margaret Greville, who bought the house with her McEwan’s inheritance (‘I’d rather be a beeress than an heiress’), and who held regular country parties for socialites from London and the wider Empire.

Portrait of Margaret Greville, Polesden Lacey

Margaret Greville collected ‘people with the unerring eye of a stamp-collector’ according to the Evening Standard, and her guests included European Ambassadors, Earls and Countesses, writers and poets – and Maharajahs. A perfect mix for an intense and suspenseful story, in which Lizzie is left wondering whether guests are who they say they are – or whether they are demons in disguise, come searching for a lost Artefact of Power.

The Lady in the Moon Moth Mask will be out in the early summer. The final book in the series (currently with numerous working titles!) will be out early next year.

Margaret loved her dogs, all of whom ended up in Polesden’s famous pet cemetery.