Her achievements were recognised in honorary doctorates from the universities of Edinburgh, Leeds, Hull, Wales and, in 1966, by her first university, Oxford. A member of the London Mathematical Society since 1928, she was its President from 1961 to 1963 and was awarded the society's De Morgan Medal in 1969. However, no list of her academic honours can give a full picture of Mary Cartwright.
At home in Northamptonshire she was a daughter of the clerical branch of a well-known local family. To begin with she was educated at home and then at the Godolphin School in Salisbury. In 1919, having already suffered the loss of two brothers killed during the First World War, she went up to St Hugh's College, Oxford, to read Mathematics. After taking a First in 1923 she taught for a time, first at the Alice Ottley School in Worcester and then at Wycombe Abbey School before being drawn back to Oxford to do research for her doctorate under G.H. Hardy, from whom she had earlier gained inspiration.
Her thesis on "Zeros of Integral Functions of Special Types" gave rise subsequently to a number of published papers on integral functions and conformal mappings. Much of this early work appears in her Cambridge Tract of 1956, Integral Functions.
In 1930 Hardy moved to Cambridge, where he worked with J.E. Littlewood. Together they contrived to bring Cartwright to Cambridge, first as Assistant Lecturer and then as Lecturer. She became resident at Girton College, where in 1930 she was elected to a Yarrow Research Fellowship. Later, in 1959, she became Reader in the Theory of Functions and she continued as an Emeritus Reader until her death.
Cartwright's partnership with Littlewood began in 1939 when they worked together on a previously intractable non- linear differential equation with much relish and enthusiasm. Although much of her work was of a severely technical nature, Cartwright had a gift for conveying the excitement of the chase to lesser beings. This particular equation, named after van der Pol, was introduced to an undergraduate audience at a meeting of the Archimedeans society with heart-warming success.
Her Girton students when she was Director of Studies in Mathematics were at first apt to find her rather frail and timid, an impression which was rapidly dispelled on closer acquaintance. Her supervision students, initially in awe of her intellectual reputation, soon thawed in the warmth of her friendship and understanding. She, who in her first year at Oxford had apparently found difficulty in her own mathematical studies, sympathised with her students' weakness. She would suggest they attend lectures given by the more colourful Cambridge characters of the time, mathematicians such as A.S. Besicovitch, truly an enriching experience. Some were invited to meet her distinguished mathematical visitors and undergraduate and research students alike benefited from such contacts.
Mary Cartwright felt strongly about mathematical education. She took a keen interest in the Mathematical Association and encouraged others to do so. She was President of the Association in 1951-52 and retained a lifelong interest in its aims.
With her pre-election as Mistress of Girton in 1948, she emerged as a shrewd and immensely hard-working head of the college when she became Mistress the following year, showing herself tireless in the endless committee work. She retired as Mistress in 1968, not wishing to become too involved in the college's centenary in 1969. In that year she was created DBE.
Mary Cartwright leaves a great mathematical legacy. Her later work is one of the foundations of the study of dynamical systems. This has in recent years been popularised in the media with television programmes on chaos and catastrophe theory.
She was painted as a college head by Stanley Spencer, who had been a contemporary of her sister at the Slade School of Art. The portrait caused enormous interest among the students in residence in Girton at the time, as the artist came to live among them while he worked. Great work though it is, it fails to convey the warmth and vitality of his subject. It is probably not possible to convey the many facets of his sitter's character, the wide gifts and sense of fun of the woman he painted. Mary Cartwright inspired energy, hard work, research and love.
Mary Lucy Cartwright, mathematician: born Aynho, Northamptonshire 17 December 1900; Fellow, Girton College, Cambridge 1930-49, 1968-98, Mistress 1949-68; Lecturer in Mathematics, Cambridge University 1935-59, Reader in the Theory of Functions 1959-68 (Emeritus); FRS 1947; DBE 1969; died Oakington, Cambridgeshire 3 April 1998.