Sandy Green was born in February 1926 in Rochester, New York, but moved to Toronto with his emigrant Scottish parents later that year.

[1][2][3] In the summer of 1944, he was conscripted for national scientific service at the age of eighteen, and was assigned to work at Bletchley Park, where he acted as a human "computer" carrying out calculations in Hut F, the "Newmanry", a department led by Max Newman, which used special-purpose Colossus computers to assist in breaking German naval codes.

[citation needed] After retiring from Warwick he became a member of the faculty and Professor Emeritus at the Mathematics Institute of the University of Oxford, in whose meetings he participated actively.

According to the Fields Medallist John G. Thompson,[5] Green showed, in two important papers,[6][7] that information about finite groups can be derived from knowledge about indecomposable modules of p-groups.

Green met his wife, Margaret Lord, at Bletchley Park, where she worked as a Colossus operator, also in the Newmanry section (Hut F).