He became a leading authority on antique clocks and his opinion and advice was sought by collectors and professionals alike. In 1940, in the early stages of the Second World War, the Air Ministry put him in charge of the Perivale Clock Company in Perivale, London.
The British clock making industry was at a low ebb, the French clock and watch making business had been almost bombed out of existence and the need for timing mechanisms was urgent. Amongst other items, fuses for anti-aircraft guns and bombs were in high demand and were manufactured at Perivale.
The Goldsmiths and Silversmiths Company were commissioned by the Ministry of Defence to undertake war work and repairs were carried out on their premises. At one time there were 150 watchmakers at the company carrying out this work and were found by Donald with the help of contacts at the Omega Watch Company who knew where the best trained staff could be found because they insisted on high standards for their appointed retail outlets. They were commandeered for war work.
During the war he flew with the RAF to neutral Switzerland to commission and purchase time pieces for the forces. On one occasion, when being entertained by one of the suppliers, his host leaned forward across the dining table and in a low voice said “if you look across to the right hand corner of the room you will see two gentlemen – the one on the left is your German counterpart”. He found it odd that next day he would be home in Pinner, Middlesex being bombed by German aircraft.
Whilst the war was on he was appointed a Liveryman of the Worshipful Company of Clockmakers and at the end of hostilities he was elected to the Council of the British Horological Institute – he was elevated to Chairman in 1956.
To give a flavour of the times post-war the following is an extract from the memoirs of George Staples who was an apprentice watchmaker at The Goldsmiths and Silversmiths Company in 1948. They were posted on the internet in 2007 but the site could not be found in 2015.
‘On my 18th birthday I received a ‘buff coloured envelope’ it was my call up papers to go into the army, I took them into Mr de Carle who said to me, you cannot go into the army now as you are more valuable here serving your apprenticeship and eventually we want to put you on government work repairing watches for the armed forces.
Mr de Carle wrote to one of the high ranking ministers a Sir Walter Monkton, K.C.M.G., K.C.V.O., M.C., KC., to obtain my exemption papers up till I was 21. These arrived and I was exempted for a while.’