In his lifetime (1883-1946) the British were ruled by "the great and the good". Keynes was one of the greatest and best of them. He loved the institutions that embraced and embodied this enlightened despotism: Oxbridge, the Treasury, the Bank of England, the BBC. The World Wars gave him opportunities to educate the taste of the masses. After the First, he persuaded Bonar Law to let him spend part of an American loan on modern French art for the National Gallery. After the Second, he perpetuated the wartime Committee for the Encouragement of Music and the Arts in the form of the Arts Council. His financial speculations made a fortune for his college; he saved Isaac Newton's manuscripts for Cambridge. The Americans (rightly) were suspicious of the uses to which the British would put the loan that Keynes negotiated in 1945. It financed Attlee's welfare socialism. Thanks to Keynes, it also paid for the Royal Opera House.

But Keynes was a man of his time and there was a strong whiff of intellectual snobbery about his generosity. Not all his listeners on the Home Service will have warmed to his battle-cry: "Death to Hollywood!" He was equally contemptuous of capitalists and workers (except for sailors), and thought both far too philistine to be entrusted with the arts or the universities. His respect for cultured Jewish friends did not preclude casual anti-Semitism. In 21st-century philanthropy, the entrepreneurial spirit of the City has supplanted Bloomsbury and its mandarin mentality. That is no bad thing. Nor is our more critical attitude to the welfare state that he made possible.

Observing him at the height of his powers and prestige during the 1944 Bretton Woods conference, the economist Lionel Robbins thought his "pure genius" comparable only to Churchill's: "Keynes must be one of the most remarkable men who ever lived." And so he was. But Robbins was seduced by his companion's aura of omniscience. Even 70 years later, we should beware of it too.