Of course, my story actually starts before all of this. I was born in the sticky heat of Durban, a port city on the eastern coast of South Africa. There I grew up hearing tales of bull sharks that were known to swim right up the freshwater rivers that meandered to the sea along the coast. I left South Africa at the age of nine, packed off to boarding school in England, but the country of my birth had struck a chord deep inside me and the stories of its sharks never quite left my mind. So when I found myself at the age of 18 with a six-month gap between finishing school and starting at university, I shot back to South Africa, delighted to have an opportunity to both be back in Africa and able to work with sharks.

I was employed at the Oceanographic Research Institute in Durban where, as an eager field biologist with a love of being out in the thick of things, I would go on field excursions in the estuaries of Zululand. We would go netting for samples and I learned even more about the unusual bull shark. I also learned that sawfishes were found swimming into rivers from the sea. My curiosity was piqued: the story of the sharks and rays that could rule the oceans and swim up rivers had caught my imagination and would not leave. It was still there, tugging insistently at the back of my mind, urging me to raise my hand when I found myself, months later, in that Cambridge classroom.

So this was how I eventually found myself in 1974 in the Casamance, a region of Senegal that shares the name of the country’s southernmost river, and right on the border with Guinea-Bissau. I was not back in South Africa, but thrilled none the less to be working on the same continent. It was on the basis of speculation by French physiologist Dr Jean Maetz that there may be sawfishes in the region that I had sailed from Marseilles in a boat loaded to the hilt with equipment. Once in Africa, I had to apply myself to hunting for the evidence to support this supposition.

I looked after Timothé’s daily needs when we were together and also paid him per sawfish caught. I calculated that by the time I had what I needed, he would have the wherewithal to buy his own canoe and motor and become an independent fisherman. But when the project ended at the close of 1975, Timothé headed for the bright lights of Dakar. He did not want to continue life as a fisherman. For about five years we stayed in touch by writing letters and then, abruptly, the communication ended.

The years rolled on and the sawfish went into a steady decline, particularly in the West African region. Decades of relentless exploitation of sharks and rays, especially by the Ghanaian fishing fleet based in The Gambia and Senegal, had led to the familiar story of a population crash. Is the sawfish, once common, now regionally extinct? Ask any local fisherman whether they have seen one and the answer is inevitably, ‘It is very, very rare’ – a euphemism for ‘It has ceased to exist.’ However, a glimmer of hope remained and I wanted to give it one last go.

So this is how I finally find myself back in the Casamance in October 2017. This time I am accompanied by my son Dominic, who is now older than I was when this adventure originally began. I am here to assess the feasibility of starting a study to find out whether sawfishes still frequent the waters of West Africa. What has happened in all the years since Timothé and I scoured the river for sawfishes?

A major part of finding those rays had come from the help of the local fishermen and their villages; fishermen like Timothé. It might be help that we’ll need again if we are to even consider trying to ascertain the status of sawfishes in the Casamance today. The need to enlist the help of the villagers aside, I simply can’t stop wondering about Timothé: where he might be and whether he is in fact alive and well.