Hilsum entered Raine's Foundation School in 1936 as the middle of three brothers, leaving in 1943 after being accepted into University College London, where he did his BSc. In 1945, he joined the Royal Naval Scientific Service, moving in 1947 to the Admiralty Research Laboratory. In 1950, he transferred again to the Services Electronics Research Laboratory (SERL) where he remained until 1964 before again moving, this time to the Royal Radar Establishment. He won the Welker Award in 1978, was elected a Fellow of the Royal Academy of Engineering, a Fellow of the Royal Society in 1979 and an honorary member of the American National Academy of Engineering. In 1983, he was appointed Chief Scientist at GEC Hirst Research Centre. He was awarded the Max Born Prize in 1987, the 1988 Faraday Medal, and from then until 1990 served as President of the Institute of Physics. In the 1990 Queen's Birthday Honours, he was appointed a Commander of the Order of the British Empire (CBE) for "services to the Electrical and Electronics Industry". He was the subject of a photograph by Nick Sinclair in 1993 that is currently held by the National Portrait Gallery. In 1997, he was awarded the Glazebrook Medal and Prize from the Institute of Physics, and is notable as the only scientist to hold both this and the Faraday Medal together. He has served as a corporate research advisor for various entities, including Cambridge Display Technology, the European Commission and Unilever. In 2007, he was awarded the Royal Society's Royal Medal 'for his many outstanding contributions and for continuing to use his prodigious talents on behalf of industry, government and academe to this day'.
