Diarmuid Downs was born in 1922 in London. His father ran a small engineering business manufacturing equipment for the oil industry. Sir Diarmuid was educated at Gunnersbury Catholic Grammar School and the Polytechnic, London. He then studied at the Northampton Engineering College, London, where he graduated with First Class honours in 1942.
He won a postgraduate bursary for further research and study, which he took up with Ricardo and Co, joining the company in November 1942, when it had re-located to Oxford as a result of its wartime evacuation from the Sussex coast.
For his initial 15 years at Ricardo, first as student, then as a member of staff, and from 1947 as Head of the Petrol Engine Department, Sir Diarmuid pursued a study of fundamental study of abnormal combustion phenomena in the petrol engine, resulting in a clearer understanding of the problems of knock and pre-ignition. Over time he became well-known and highly respected amongst Ricardo clients, and in the automotive industry in general. He would regularly give a technical address to large numbers of attendees at the SAE Detroit Congress.
During the 1950s, Sir Diarmuid won three Institution prizes for his research: the George Stephenson Research Prize and the Crompton Lanchester Medal in 1951, and the Dugald Clerk Prize the following year.
Sir Diarmuid spent his entire career at Ricardo. He became a member of the Board in June 1957, and Managing Director in 1967. He was also involved in the purchase of G Cussons Ltd in May 1964, becoming its Chairman. He was appointed Joint Chairman and Managing Director of Ricardo in 1976, taking over the Chairmanship from Jack Pitchford, and he remained Chairman until 1987.
Away from Ricardo, he sat on a number of boards: he was a member of the Advanced Council for Applied R&D from 1976-80; a member of SERC from 1981-85 and the Design Council from 1981-89. He was on the Boards of both the Society of Automotive Engineers Inc, from 1983-86, and the British Council from 1987-1993, while between 1988 -1993 he was a Member of the Advanced Board of the Parliamentary Office of Science and Technology.
He was a member of the Council at City University from 1980-1982, a visiting fellow at Lincoln College, Oxford from 1987-88, and Pro Chancellor of Surrey University from 1992-1994..
In 1978, Sir Diarmuid became President of the Institution of Mechanical Engineers in 1978. A Fellow both of the Royal Society and the Royal Academy of Engineering, Sir Diarmuid was made a CBE in 1979 and received his knighthood in 1985. Since 1984, Sir Diarmuid had been a Liveryman in the Worshipful Company of Engineers.
Sir Diarmuid published numerous papers on internal combustion engines in the British and international engineering journals and conference proceedings. In 1999, he gave the foreword to John Reynolds’ book Engines and Enterprise: the life and work of Sir Harry Ricardo. He wrote: “I had the great privilege of working for Sir Harry Ricardo for the last thirty years of his life, first as a young engineer and eventually as his chosen successor as head of the company. His staff..in continuing and building on [his] achievements benefited from the comments and guidance of Sir Harry himself, right up to his death in his ninetieth year. Sir Harry was a fine engineer and a delightful man. The story of his life.. has lessons and fascination for us all."
An epitaph, which family, friends, colleagues and members of the Institution would agree is just as fitting for Sir Diarmuid himself.
Sir Diarmuid leaves his wife and their four children.