Born in Asnières-sur-Seine, Hewitt studied the violin at the Conservatoire de Paris.
[3] Here he released six albums until 1942, including the first recording of Jean-Philippe Rameaus Six Concerts en Sextuor.
From 1940 Hewitt was active in the Resistance, where he belonged to Colonel Maurice Buckmaster's network.
In November 1943 he was denounced and arrested and held in Fresnes and Compiègne, then in 1944 deported to the Buchenwald Concentration Camp, arriving on 29 January (prison number 44007).
[7] On 2 November 1945, he conducted Fauré's Requiem at an event held at the Palais de Chaillot, ‘In memoriam: concert in memory of political deportees who died for France’, by the Orchestre national et choeurs de la Radiodiffusion Française (dir.