It is appropriate to approach Keynes's investment career by dividing it into the same two parts that prove useful in discussing many of his other activities—up to his resignation from the Treasury in June 1919, and afterwards.

In the earlier period, Keynes was operating on his own account on a modest scale and providing investment advice for his friends. His dealing activities were limited and most of the increase in the value of his portfolio came from savings. After 1919, on the other hand, Keynes was operating in financial markets on a very much larger scale, both on his own account and on the account of others. For example, Keynes was a Bursar of King's College, Cambridge, Chairman of the National Mutual Life Assurance Society (1921–38), a director of the Provincial Insurance Company, a director of various investment trusts—the Independent Investment Company (1923–46), the A.D. Investment Trust (1921–7), the P.R. Finance Company (1924–36, Chairman 1932–6)—and an instigator of the Syndicate of 1920. During these years his income came to depend much more on his financial than his academic activities, as Table 1 indicates.

In what follows, I shall first concentrate on Keynes's activities as an individual investor over both periods, before looking more widely to the financial dealings which he undertook in collaboration with other, equally forceful personalities in the City, and on behalf of King's.