Apparently the chief ran a special investigative unit for a department of the French secret service that no one was allowed to know about. I arrived punctually for my meeting, hoping I was dressed elegantly enough to impress an important spy. The entrance to the office building near the Bastille was nondescript but the foyer was discreetly protected by cameras, burly receptionists and security codes. What does a French secret policeman look like? I wondered. Maybe I should have reread The Day of the Jackal. I was collected by a scruffy plainclothes man, wearing the sort of jeans and trainers you can run fast in and, although it was a very hot day, the sort of bulky jacket that can disguise a weapon. I tried to keep up in my smart high heels as he hurried me through several doors protected by PIN codes. I had had to walk miles already that day, and my comfortable shoes were secreted in my briefcase.

The secret police chief had a very big office. He wore a smart Armani-style suit, and smoked a large noxious cigar. He was tall, thin and elegant, with sad, rather anxious eyes. He shook my hand and immediately asked me to tell him the facts. As he had heard the story already from my friend, he wanted only a factual resumé from me – and very speedily. Since the facts were so sparse, this did not present a problem. I had the distinct impression that I had only a brief slot in his overcrowded timetable. As I fumbled to bring out the bottle, which I had brought with me in case he needed hard evidence of the truth of my tale, he summoned a deputy to sit in on the interview.

The deputy was a more down-to-earth type. In his early fifties, tubby, experienced, tough, he looked as though he had seen it all. He lit a cigarette and the fug of Gauloise and cigar smoke thickened the air and caught at my throat; I had the strangest sensation of having strayed into a film noir. The deputy twiddled his greying moustache as he listened to my bald statements. The first name, the age. ‘Madame,’ he said, echoing the French private detective, ‘you simply don’t have enough clues.’

The boss interrupted him. ‘Madame is a good friend of a good friend,’ he told his deputy with a meaningful look. ‘We will do all we can to help.’ The deputy refocused. ‘It is not a question of money,’ the boss added, raising his hand as though to wave away a bribe. I hid my surprise, since it had never occurred to me to offer one, and I would not have known how to go about suggesting it, or, given his expensive taste in suits, have been able to afford his charge. He started to read the letter while I summarized my efforts so far, brushing over the meetings with the astrologer and the tarot card reader.