I have been reading a very interesting book by Kevin Theakston After Number 10. In the States, the notion of an effective post-presidency was really invented by Jimmy Carter who seems to have made a more positive impact once he left office. There are analogies in Britain, Balfour being a prime example.
Some of the least successful prime ministers have enjoyed life much more after leaving office, examples including Sir Alec Douglas-Home, who returned to office as Foreign Secretary, and Sir John Major who has developed a series of business roles and enjoyed his cricket. Hinterland seems to be important. For those for whom politics was the centre of their lives, such as Harold Wilson and Margaret Thatcher, the adjustment has been much more difficult.
What is certainly the case is that prime ministers no longer have financial problems once they leave office. Asquith had to be helped out by his friends, as did Churchill (who admittedly was a big spender) and Attlee left very little money. These days not only is there the autobiography, but also the chance to make big bucks on the American lecture circuit.
Gordon Brown is not, of course, in the book. But he said that he intends to devote himself to his constituents and to international development work, particularly in Africa where he has been this weekend.