John Keene was born in Birmingham in 1921. He was educated at King Edward’s School, Birmingham, and the University of Birmingham. He is best known for his work in Manchester at the Christie Hospital on pulse radiolysis equipment.

During the Second World War he was involved in the development of the magnetron, used to intercept bombers and submarines during the conflict. After successfully completing this project, Keene moved to the USA where he worked on the electromagnetic separation of uranium-235, an important part in the development of the atomic bomb.

After the war he studied for a PhD at Cambridge University. His thesis examined charge exchange and ionisation in gas discharge. In 1949 he joined Charles Gilbert's team at the Christie Hospital, Manchester, working on the clinical use of radioisotopes. Keene was also free to follow his own research interests and to collaborate with other teams at the Christie. He joined Walter Dale's team in studying radiation chemistry in relation to radiobiological processes, bringing mathematical expertise to the research. Dale's team theorised that highly-reactive, short-lived chemical intermediates, of the type produced in the body during radiation treatment, produced fast reactions, but couldn't prove the hypothesis. Between 1955 and 1959, Keene developed equipment for use with the electron accelerator at AEI in Trafford Park, Manchester. This equipment used single pulses of electrons to detect the intermediates optically, and so proved Dale's hypothesis. Keene's spectrophotographic method of detection became commonly used in radiation chemistry, replacing the spectrographic method.

During the 1960s, Keene further developed his measuring apparatus, working with the Radiation Division of Vickers-Armstrongs Ltd, Swindon. The apparatus was installed at the Paterson Institute for Cancer Research, based at the Christie Hospital, in 1967. Known as the Paterson Linac, the equipment was a very powerful source that produced a lot of intermediates at once, mostly free radicals. Keene's development of pulse radiolysis revolutionised radiation chemistry, becoming an important fast reaction technique for studying unstable species and free radicals. Variations on his equipment were used in laboratories around the world. His research and development of the pulse radiolysis equipment earned him the Weiss Medal of the Association for Radiation Research in 1978. The Paterson Linac was decomissioned in 2000, with the main part of the apparatus going to Daresbury Laboratory to enable studies on pulse radiolysis to continue there.

Keene retired in 1986, but continued to provide advice to fellow scientist developing instrumentation techniques.

He died while on holiday in Malaysia in 1991.