Godfrey Hounsfield, the inventor of the CT scanner, was the epitome of the brilliant boffin – modest, retiring and shunning the limelight. He was born on 28 August 1919, the youngest of the five children of Thomas Hounsfield, a steel engineer who took up farming in Newark-on-Trent, Nottinghamshire. There Godfrey grew up surrounded by farm machinery, with which he became fascinated. ‘In a village there are few distractions and no pressures to join in at a ball game or go to the cinema and I was free to follow the trail of any interesting idea that came my way. I constructed electrical recording machines; I made hazardous investigations of the principles of flight, launching myself from the tops of haystacks with a home-made glider; I almost blew myself up during exciting experiments using water-filled tar barrels and acetylene to see how high they could be waterjet propelled.’ At Magnus Grammar School he was interested only in physics and mathematics. At the outbreak of the Second World War he joined the RAF as a volunteer reservist and was taken on as a radar mechanic instructor, occupying himself in building a large-screen oscilloscope. His work was noticed by Air Vice Marshall Cassidy, who got him a grant after the war to attend Faraday House Electrical Engineering College, where he received a diploma. He then joined the staff of EMI working on radar and guided weapons, working with primitive computers. In 1958 he led a team building the first all-transistor computer, speeding up the transistors by providing them with a magnetic core. In 1967 he began to study aspects of pattern recognition and worked in the Central Research Laboratories of EMI. Contrary to the public relations story, which has been repeated so often that it has come to be accepted as true, his idea did not occur to him when out walking, and it was not supported by the full resources of EMI. His colleague, W E Ingham, pointed out that EMI were not interested: they were not in the medical business, and it was only covertly that a deal was done with the Department of Health and Society Security to fund the development of what became the first CT scanner. The first brain to be scanned was that of a bullock. The prototype was soon shown to be successful in 1971, when it was used to diagnose a brain cyst at Atkinson Morley’s Hospital and before long Hounsfield’s work had been plagiarised and developed all over the world, mostly overseas. Hounsfield was unaware that Cormack, of Tufts, had published theoretical studies on the mathematics for such a device. A whole-body scanner was introduced in 1975. Honours came thick and fast: CBE, FRS, the Nobel prize (shared with Cormack), a knighthood and an honorary FRCS. He remained a modest, retiring bachelor. His advice to the young was: ‘Don’t worry if you can’t pass exams, so long as you feel you have understood the subject.’ In retirement he did voluntary work at the Royal Brompton and Heart Hospitals. He died from a chronic and progressive lung disease on 12 August 2004. He was unmarried.