Sir John Turton Randall, FRS FRSE[2] (23 March 1905 – 16 June 1984) was an English physicist and biophysicist, credited with radical improvement of the cavity magnetron, an essential component of centimetric wavelength radar, which was one of the keys to the Allied victory in the Second World War.

It not only changed the course of the war by allowing us to develop airborne radar systems, it remains the key piece of technology that lies at the heart of your microwave oven today.

Randall's deputy, Professor Maurice Wilkins, shared the 1962 Nobel Prize for Physiology or Medicine with James Watson and Francis Crick of the Cavendish Laboratory at the University of Cambridge for the determination of the structure of DNA.

From 1926 to 1937 Randall was employed on research by the General Electric Company at its Wembley laboratories, where he took a leading part in developing luminescent powders for use in discharge lamps.

[2] By 1937 he was recognised as the leading British worker in his field, and was awarded a Royal Society fellowship at the University of Birmingham,[citation needed] where he worked on the electron trap theory of phosphorescence in Mark Oliphant's physics faculty with Maurice Wilkins.

Oliphant put Randall and Harry Boot on this issue of producing a microwave oscillator, asking them to explore miniature Barkhausen–Kurz tubes for this role, a design already used for UHF systems.

In the case of the magnetron, the resonator was replaced by two metal plates held at opposite charges to cause the alternating acceleration, and the electrons were forced to travel between them using a magnet.

The magnet would cause the electrons to travel in a circle, as in the case of the magnetron, so they would pass by each of the resonators, generating microwaves much more efficiently than the plate concept.

[10] Developed using common lab equipment, the first magnetron consisted of a copper block with six holes drilled through it to produce the resonant loops, which was then placed in a bell jar and vacuum pumped, which was itself placed between the poles of the largest horseshoe magnet they could find.

GEC introduced a number of new industrial methods to better seal the tube and improve vacuum, and added a new oxide-coated cathode that allowed for much greater currents to be run through it.

[citation needed] In 1944 Randall was appointed professor of natural philosophy at University of St Andrews and began planning research in biophysics (with Maurice Wilkins) on a small Admiralty grant.

[citation needed] During his term as Director the experimental work leading to the discovery of the structure of DNA was made there by Rosalind Franklin, Raymond Gosling, Maurice Wilkins, Alex Stokes and Herbert R. Wilson.

[13] Maurice Wilkins shared the 1962 Nobel Prize for Physiology and Medicine with James Watson and Francis Crick; Rosalind Franklin had already died from cancer in 1958.

[2] In 1951 he set up a large multidisciplinary group working under his personal direction to study the structure and growth of the connective tissue protein collagen.