He was the son of the Rev. Arthur H. Bray (22 October 1886 - 9 September 1974; e.m. 1911), a missionary from 1914 to 1940 and 1949 to 1952 in the South China District. Born in China on 29 June 1930, he was educated at Aberystwyth Grammar School and Kingswood School. At Jesus College, Cambridge 1949-1952, he gained a double first in pure maths and was SCM president 1951-1952. He was awarded a Choate Fellowship at Harvard in 1955. From 1956 to 1962 he gained industrial experience with ICI. As Labour MP for Middlesbrough West 1962-1970 and for Motherwell and Wishaw 1974-1997, he was the first Labour politician with scientific training for decades. He was a highly intelligent, sincere and deeply committed MP, whose scientific and technological expertise came into play when he was in office: as Parliamentary Secretary in the Ministry of Power and then in the Ministry of Technology. His book on Decision in Government (1970) led to his reignation from office. From 1992 to 1997 he served on the Science and Technology Select Committee. He was prepared to be critical of the Labour Party and of Britain for its failure to invest in technological research. Until its closure in 1992, he vigorously defended the threatened Ravenscraig steel works. He was a local preacher for over 50 years and his Methodist roots influenced his political stance, especially in the face of moves towards easier divorce and abortion in the permissive society.
He was chairman of the Fabian Society, served on the British Council of Churches and from 1972 was deputy chairman of Christian Aid from 1972 to 1984. He died on 31 May 2002 after a long coronary illness. His autobiography, Standing on the Shoulders of Giants (2004) was published posthumously.