In 1948, the young biology teacher started his career at Dauntsey's, an independent boarding school in Wiltshire, using an ancient cyclostyle machine to reproduce drawings to illustrate his lessons.
After several years of amassing laboriously produced drawings, it occurred to him they might make a useful teaching aid, as there were few well illustrated biology books.
But he might not have succeeded without the intervention of a pupil, the son of the artist who illustrated School Science Review. The boy told his dad that his science teacher was writing a book (which wasn't quite true) and he told Kenneth Pinnock, then educational manager at publishers John Murray. That was in 1958 and proved to be the start of a long publishing partnership.
His first book, Introduction to Biology, took three years to write and illustrate and a further three to get published. The days of the cyclostyle were behind him and the book was produced on the latest web-offset technology, enabling line drawings and photographs to be printed together, rather than the photos being relegated to a few pages bound into the centre of the book. It was also a big book, allowing large, clear illustrations.
Sales took off and the book was translated into several languages. In 1968, Don became a part-time teacher and finally "retired" to write full-time. Since then, there have been five editions of Introduction to Biology.
Mackean wrote other books, including GCSE Biology, which was first published in 1986; the new second edition has been produced in response to the changes brought in by the national curriculum.