Huge thanks to brilliant Ali Dougal and the fantastic team at Egmont for all their support and enthusiasm for Sophie and Lil’s latest exploits. In particular, special thanks to Sarah Levison and Sara Marchington, and to the absolute dream team of illustrator Karl James Mountford and designer Laura Bird for the stunning design.

Researching this book was quite a task, and although there are far too many to name here, I would like to acknowledge my debt to the writers and historians who have written about pre-revolutionary Russia. Thank you also to all those who kindly shared their stories and advice on visiting St Petersburg with me – in particular Katherine Rundell, Hazel Wigginton and Donald Lamont.

As always, enormous thanks go to my parents for all their support, and to my friends – especially Nina Douglas, who patiently helped me unravel a sticky problem involving crates and cellar windows. Thank you also to my husband Duncan, who for this book put up with a lot of long conversations about the intricacies of early 20th century Russian politics.

Spies in St Petersburg is dedicated to my wonderful agent and friend Louise Lamont, who went above and beyond the call of duty for this book, joining me on a research trip to Russia. As well as boldly leading the way around St Petersburg, walking over 60 miles in six days, and selflessly helping me taste all the Russian delicacies we could find, she even taught herself Russian for the occasion. Without her this book would certainly not be what it is (and I would quite possibly still be wandering St Petersburg in confusion, failing to decipher Cyrillic street signs and unsuccessfully trying to order cakes). Luckily I did managed to learn one very appropriate Russian word: Cпасибо – thank you.

Finally, a very special thanks to all the booksellers, librarians, teachers and readers (of all ages) who have so enthusiastically embraced Taylor & Rose Secret Agents and this new phase of Sophie and Lil’s adventures.