I’d like to thank my historical consultant, Andro Sillar, whose knowledge of Scottish history, culture and attention to detail were invaluable. A true Caledonian, he has proved to be as inspiring and mysterious as the erudite Mr Petrie, prompting me to wonder if our paths crossing were more than a happy coincidence. Great appreciation goes to the Lataoui children: Lamis, Lina, Yumna and Youssef, who spent a wonderful day with me immersing themselves in the world of Sweetheart and Mr Petrie, emerging from piles of paper with helpful feedback when it was most needed. Of course, family always plays a major role and influence, and I’m indebted to mine, especially my daughter, Daisy Jane, who injected a bit of technology and 21st-century thinking while my beloved husband, Samir, sat and listened patiently as the story of the Caledonians unfolded. His butter to my bread was the gentle words of encouragement he spread during periods of literary doldrums.