His godfather and cousin was Sir Archibald Sinclair, Viscount Thurso, leader of the Liberal Party and Secretary of State for Air in Winston Churchill's wartime cabinet.
Sinclair decided that what Sir William Jameson, Chief Medical Officer of the Ministry of Health, would find most useful were "half-page" survey-backed assurances that the indications were that the nation's nutritional status was satisfactory, rather than detailed papers, suitable for submission to recognised peer reviewed scientific journals.
Part of the work of the Oxford Nutrition Survey was carried out by a small mobile team, which was sent to industrial towns, such as Accrington, Merthyr, Chesterfield, and Dundee.
Following hectic preparations, Sinclair and his team went to the Netherlands as the Nutrition Survey Group SHAEF (Supreme Headquarters Allied Expeditionary Force), just before the German surrender.
The state of the famine needed to be assessed, treatment and response recorded, and the results set out to inform future action in similar circumstances.
In 1954, Hans Adolf Krebs succeeded Sir Rudolph Peters as Professor and Head of the Department of Biochemistry, to which the Laboratory was transferred and closed shortly thereafter.
In 1956 Sinclair made his most widely known contribution to nutrition in the form of a letter to The Lancet, entitled "Deficiency of essential fatty acids and atherosclerosis, etcetera".
The causes of death that had increased most in previous years were lung cancer, coronary thrombosis, and leukemia and Sinclair believed essential fatty acid (EFA) deficiency to be important in all three.
Phospholipids containing abnormal fatty acids are also less easily eliminated and so are retained in the plasma and increase the coagulability of blood, thereby contributing to coronary and cerebral thrombosis.
In 1958, the first election period for Sinclair's Readership ended, and he was not reappointed, presumably because his contribution to the traditional scientific literature was judged to be insufficient, in spite of the broad sweep and originality of his thinking.
Sinclair was no longer a member of the Department of Biochemistry, but he continued to tutor at Magdalen and, because of his reputation as an inspiring and entertaining speaker, he was invited to lecture widely.
In 1976, he was able to spend some time joining the expedition of Bang and Dyerberg in northwest Greenland, which led to his most widely known experiment, in which he put himself on an Inuit diet, consisting solely of seal, fish (including molluscs and crustaceans), and water for 100 days, starting in March 1979.
The experiment was a dramatic demonstration of the importance of long-chain fatty acids of fish oils in decreasing the aggregation of platelets and thus the incidence of thrombosis.
Lord Porritt was invited to join the council, the composition of which changed over the years: Sinclair had plans drawn up for a substantial institute to be built at Lady Place.
It was to incorporate laboratory facilities for fifty workers, together with a lecture theatre, a museum, offices, and a library to house his collection of some 300,000 reprints and books, including those of Sir Robert McCarrison, Surgeon-Captain Thomas L. Cleave [1], Neil Painter, Hugh Trowell[2], and Cicely Williams.
Much of his time was occupied in trying to raise funds, but the operation of the institute in the temporary accommodation arranged at Lady Place was heavily dependent on personal financial donations from Sinclair.
The Council of Management decided not to assume direct responsibility for the development of research at Lady Place, but to see whether a university would wish to further Sinclair's aspirations by founding a chair in Human Nutrition.