Over the next few weeks I tried once or twice more to place an advert and was always put on hold for the editorial department who never called back. Whoever thought it would be so hard to spend money advertising for information?

The published article in La Voix du Nord finally arrived in the post, several weeks after it had appeared. It was satisfyingly large, carried the photograph and a plaintive article beneath, and my email address, correctly spelt, at the bottom. It had attracted absolutely no response – neither to me nor to the newspaper.

When, after blocking my frequent attempts at advertising, Le Figaro failed to act on its initial interest, I decided to try another medium. I emailed the main Calais radio station, in what I thought was a suitably upbeat, casual manner:

Hello, I am writing to you from London. I found a bottle on an English beach with a letter in French in it. Who is Maurice, died aged thirteen? The letter haunts me. Can you ask your listeners for information?

I followed up on the telephone and initially the producer seemed very interested. However, an urgent deadline was always looming, and after being fobbed off a few times, my enthusiasm waned.

I knew I was reaching the end of the road. Stopping now felt like mislaying a gripping thriller thirty pages from the end, just before discovering whodunnit. But I had no choice. I had no idea how to get on French television and it seemed there was no other way of finding the letter-writer. My friend the dog-walker rang for a chat and asked me how the search was going. I told her it was over. I had done everything I could. I had spent time, money and energy talking to endless statisticians, detectives, journalists, an astrologer and a tarot reader. I had got it out of my system, the scab had been picked, now I was going to try and leave it to heal. I was irritable. I almost blamed my friend for having shown me the letter in the first place. ‘It was an awful letter,’ she said. ‘I only read it twice. It upset me so much I had to put it away. I’ve never looked at it since.’

As I put the telephone down I realized that the unknown mother and her grief had almost faded away in the excitement – and more recently the boredom – of the chase. In the excitement of meeting detectives and astrologers, of hunting through archives, and chasing round ribbon shops, I had somewhere let slip the essential tragedy.