The German British mathematician Walter Ledermann described in his memoir how, as an assistant in Mathematics, he met the biology Professor Thompson at St Andrews in the mid 1930s and how Thompson "was fond of exercising his skills as an amateur of mathematics", that "he used quite sophisticated mathematical methods to elucidate the shapes that occur in the living world" and "[...]differential equations, a subject which evidently lay outside d'Arcy Thompson's fields of knowledge at that time." Ledermann wrote how on one occasion he helped him, working and writing out the answer to his question.