John Maynard Keynes (1883-1946) was one of the greatest thinkers of the twentieth century. No one disputes that his ideas had a revolutionary impact on economic theory and created what was essentially a new orthodoxy.

His most extraordinary achievement, however, must surely be the durability of his influence. The validity or otherwise of Keynesian economics continues today to be the subject of passionate debate among economists worldwide. Well over sixty years after publication of the General Theory of Employment, Interest and Money (in 1936) his ideas still have the power to invigorate the thinking of successive generations. Keynesian thought is often disputed but never ignored. It is the starting point for almost any serious consideration of how we think about economics, not as an isolated specialism but inseparable from politics, history, philosophy and psychology.

Keynes was a man of many parts. His wisdom drew strength from his enormous practical experience. He was a practicing as well as a theoretical economist, a man of international affairs, a member of the Bloomsbury Group, a major writer, an outstanding editor, a book and paintings collector and, not least, a businessman. He left behind a huge collection of papers that record and illuminate all these facets of his career, interests and activities for every period of his life.

The letters, for instance, are to and from more than 4,000 correspondents. A sampling of their names reads like an intellectual hall for fame. And his personal papers offer fresh insights into the development of Keynes 'vision of what true economic and social progress should be.