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Percy John Heawood (8 September 1861 Newport, Shropshire, England[1] - 24 January 1955 Durham, England[2]) was a British mathematician educated at Queen Elizabeth's School, Ipswich, and Exeter College, Oxford.

He spent his career at Durham University, where he was appointed Lecturer in 1885. He was, successively, Censor of St Cuthbert's Society between 1897 and 1901 succeeding Frank Byron Jevons in the role, Senior Proctor of the university from 1901, Professor in 1910 and Vice-Chancellor between 1926 and 1928. He was awarded an OBE, as Honorary Secretary of the Preservation Fund, for his part in raising £120,000 to prevent Durham Castle from collapsing into the River Wear.

He devoted essentially his whole working life to the four colour theorem and in 1890 he exposed a flaw in Alfred Kempe's proof, that had been considered as valid for 11 years. With the four colour theorem being open again he established the five colour theorem instead. The four colour theorem itself was finally established by a computer-based proof in 1976.

Writing in the Journal of the London Mathematical Society, G A Dirac, wrote:

In his appearance, manners and habits of thought, Heawood was an extravagantly unusual man. He had an immense moustache and a meagre, slightly stooping figure. He usually wore an Inverness cape of strange pattern and manifest antiquity, and carried an ancient handbag. His walk was delicate and hasty, and he was often accompanied by a dog, which was admitted to his lectures. ... His transparent sincerity, piety and goodness of heart, and his eccentricity and extraordinary blend of naiveté and shrewdness secured for him not only the fascinated interest, but also the regard and respect of his colleagues.[3]

He was fond of country pursuits, and one of his interests, unusual for a mathematician, was Hebrew.[4] His nickname was "Pussy".[5] He was a cousin of the physicist Sir Oliver Lodge.

Durham University awards an annual Heawood Prize to a student graduating in Mathematics whose performance is outstanding in the final year.