My best subjects were languages and history, my weakest maths, physics and chemistry. As a result of considerable paternal pressure, I chose science A-levels, but probably my most important achievement in chemistry was to manufacture explosive nitrogen tri-iodide crystals and place them on the path into the assembly hall along which the masters walked each morning. Those gathered thoroughly enjoyed the resulting explosions under the feet of the parading masters.
Biology exams were based on static anatomical drawings and studying live animals was not part of the programme.
But when our regular teacher became ill, the school employed Robert Mash, a graduate student, to teach us some aspects of biology. Bob Mash was then a student of Niko Tinbergen, the eminent zoologist, and studied the displays of black-headed gulls. He was laconic and witty and he largely disregarded the syllabus. He encouraged the half a dozen or so of us doing A-level biology to read and write about animal behaviour, evolution, and related areas. His take on biology resonated with my own interests: for the first time I wanted to read more. His teaching provided excitement and stimulation.
He talked about how you understand the behaviour; the adaptive mechanisms that animals adopt. He was much younger and more informal than the other teachers, with a sardonic style. His approach was just to tell us something interesting. He hadn't prepared, but his love of the subject and enthusiasm shone through.
The topics he covered became the platform for my later career. My father quickly arranged for me to spend the last two summer vacations of my school years as a technician at the Max Planck Institute in Bavaria, directed by Konrad Lorenz and Jurgen Aschoff.
My career in ethology (the study of animal behaviour) was born, but not before rejections: my A-level marks were pretty abysmal - certainly not good enough to get into Oxford in the present competitive environment.
Professor John Krebs, Lord Krebs is an expert in zoology and bird behaviour. He was the first chairman of the Food Standards Agency and is now principal of Jesus College, Oxford. He was speaking to Ginny Russell.