This photograph shows Abram Samoilovitch Besicovitch (b. 1891) mowing Trinity College lawns during the Second World War. Originally from Russia, Besicovitch came to Cambridge as a lecturer in 1927, was made a fellow in 1930 and was later appointed Rouse-Ball Professor of Mathematics (1950-58). He died in Cambridge in 1970.
For more biographical information see the Trinity College Chapel Website.