John Michael Hammersley

Founder of the mathematical theory of percolation
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Hammersley was born at Dee Bank, Helensburgh on 21 March 1920. He was born of an international couple. His father, Guy Hammersley, was employed in the American steel trade mostly in London, and worked his way from office boy to European Manager during the 1920s. His mother, Marguerite Whitehead, was born in Moscow in 1889, and was sent to boarding school in England in 1903.

John was sent to Sedbergh in 1934, and, finding himself bored by the traditional classical education on offer there, he migrated to science and mathematics. He was awarded a scholarship at Emmanuel College, Cambridge. War intervened and, called up in 1940, Hammersley was commissioned in 1941 in the Royal Artillery. Posted to an anti-aircraft gun site near Worsham, he applied himself to the use of wireless and radar in gunnery, and introduced several improvements on current practice in gunnery calculations with immediate benefit to accuracy. Realising that there were greater errors elsewhere, he replaced the old seven figure trigonometric tables by four figure tables. He graduated in 1948 as a Wrangler (‘First Class’). It was over Sunday lunch in Oxford that he met Gwen Bakewell, who became his wife in 1951. Hammersley was appointed to Trinity College where he remained a Fellow until his death. He spent some years commuting to Harwell before returning in 1959 as a Senior Research Officer in the Institute of Economics and Statistics. He was a regular contributor to the Berkeley Symposia on Mathematical Statistics and Probability. He received many honours, including election to the Royal Society in 1976.

Hammersley was a pioneering mathematician of enormous intellectual power. He was passionately involved in creating mathematics for modelling and solving practical problems. Despite his love of rigorous analysis, he did not hesitate to turn when necessary to calculators, and he was a master of the mechanical desk calculator and the early computer. He once boasted of holding the 1961 world record for keeping a computer (at Bell Labs) working without breakdown for 39 hours.

An area which he made his own is that termed ‘Monte Carlo simulation’, this is a general technique first attributed to Stan Ulam in his work on the nuclear bomb at Los Alamos. With David Handscomb, Hammersley developed the basic theory and published the standard work. Their book Monte Carlo Methods (1964) remained for many years the only work available to practitioners, and the techniques therein are used currently in banks and elsewhere throughout the World.

During his career he held visiting positions at Princeton University, the University of Illinois (Urbana), Bell Laboratories (Murray Hill), and the University of California (Berkeley). He was awarded an ScD by Cambridge University (1959), the von Neumann medal for applied mathematics by the University of Brussels (1966), the gold medal of the Institute of Mathematics and its Applications (1984), and the Pólya prize of the London Mathematical Society (1997).

John Hammersley died on 2 May 2004 at the John Radcliffe Hospital, Oxford, from pneumonia and cerebrovascular disease. He was cremated on 10th May at the Oxford crematorium, following a memorial service in the chapel of Trinity College, and was survived by his wife and two sons.