A couple of readers had specific tips: a neighbour of their mother’s called Jeannette (the letter that the medium had identified as being the first initial) had lost a child called Maurice during the last years of the war. Later the mother had emigrated to Cap Vert and the correspondent suggested that she had perhaps written the letter in the bottle when leaving the land where her first son was buried. The correspondent planned to wade through all her past letters in case she had received a letter or a card from Jeannette so that we could compare the handwriting. Another thought he had heard something about a similar bottle while working on a patrol boat for the Lighthouse and Radio Beacon Service in Brittany.

One girl sent me a scan of a sad letter dated February 1946 that she had found under a floor board in her parents’ attic, saying she had been inspired by my search to seek out the author and return the letter to him, though it seemed likely that too many years had passed. An eighty-five-year old gentleman sent me a beautiful graph of the letters he had sent in bottles. Between 1984 and 2004 he had sent nearly 1500 bottles, receiving 258 replies, an 18% success rate. The graph tabulated the country of origin of the reply – top place to Algeria with forty-nine, closely followed by France and Tunisia – and the time of receipt, with 1992 being a vintage year of twenty-four replies.

Only one reader strongly disapproved. A Swiss man emailed to say how shocked he had been at my search, and asked me how I had dared to hunt the mother like prey when she had clearly sought anonymity and closure. Perhaps he was right.

Many told me of their emotions on reading the book; how moved they had been by the letter, or of how it had helped them in some way. Some wrote how they too had lost a child, or simply how they had come to appreciate their children more after reading of the heartbreaking loss of the young boy.

But mostly there were those who simply wanted to know if there had been any progress, to request an update, to put down a marker that I should let them know if the story were to reach a definite conclusion at some point in the future. As I read the letters, and sent back short responses, I was just waiting for the call from the unknown mother. Could she forgive me enough to get in contact directly, to let me speak to her and try to explain?

Then, almost one month to the day after the first contact, the psychologist rang me again. ‘She is ready. You can ring her.’