He died the day after learning that his arguments against the use of plastic insulators - which he regarded as not sufficiently tested - for new rail electrification by Railtrack and Virgin Rail, had been turned down.
Looms held patents for more than 100 inventions. They ranged over a wide variety of electrical applications, including new methods of paint-spraying for cars. On retiring from the Central Electrical Research Laboratories (CERL) at Leatherhead in 1980, he became an internationally renowned consultant. He wrote what became the standard textbook on high power transmission and insulators, Insulators for High Voltages (1988). Though not translated into Japanese, this now circulates widely in Japan in pirate editions.
John Looms was not destined for a career in science. His father, in the 1930s depression, thought he should opt for security in the civil service, preferably as a barrister, as he believed that there would always be jobs prosecuting criminals. The Second World War intervened and Looms served in radio and signals. His own war aim, according to his family, was to get to Scandinavia. Having seen Ingrid Bergman in Casablanca he declared "I'll have one of those", and ended up in Denmark where he met his future wife, Karen Bergreen.
After the war he worked first in the Inland Revenue but studied by night at Birkbeck College, London, taking an external degree in Physics. In 1951 he joined the National Physical Laboratory at Teddington. Nine years on, wanting to work in a field which had a more immediate application to people's lives, he moved, still a civil servant, to the CERL. Several of of his former colleagues who had at first deplored his move away from "pure science" followed.
Looms did much of his work on insulators at what he claimed was the "most polluted of all spots", the test site at Brighton Power Station at Shoreham; it boasted a mixture of sea fogs, salt winds and industrial smoke. While here, he worked out the internationally accepted Seafog Test - subjecting insulators to prolonged testing under the most adverse conditions to see how long they lasted before "flashing over" (a miniature lightning discharge).
Always in his mind was the human benefit of his work. His vandal-proof insulators' chief merit, in his eyes, was that they eliminated danger to vandals - children throwing stones and sticks in the hope of breaking them.
"Live" working on power lines, doing repairs without switching the current off, had considerable economic benefits. Looms rigorously tested everything himself before allowing others near. He is believed to have been the first man anywhere to have worked with bare hands on overhead power lines at 400,000 volts. He achieved it with plastic chains to insulate the repair worker and metallised suits to protect against corona discharge from the live lines.
It was his concern for people's well-being which led to John Looms's opposition to what he believed was the insufficiently tested use of plastic in railway insulators. Trials in the American prairies and the Australian outback, he believed, should not be extended to Britain's densely populated railside urban areas, where the collapse of a high-voltage line across houses or a road could have appalling consequences.
John Sidney Thomas Looms, electrical engineer: born London 3 August 1918; married 1947 Karen Bergreen (one son, one daughter); died East Molesey, Surrey 24 May 1998.