Kevin Theakston: Brown begins his adventures in the afterlife

Some prime ministers with short and unsuccessful stints in office have gone on to have a lengthy and successful afterlife, while some of those higher up the "league table" of prime ministerial achievement have quickly faded into the background. Although battered and exhausted after three years in Number 10 and a decade at the Treasury, Brown is only 59 and he can expect to remain active for some time yet, with ideas, energy and something still to prove.

The political waters can close quickly over the departed prime

minister. Some, like Attlee, Eden and Wilson, disappeared from the political scene. Others have a "second act", carving out a continuing role in politics and public life. Sometimes this has been a constructive role, but not always. Macmillan warned against "hanging around the greenroom after final retirement from the stage". Heath and Thatcher were examples of "how not to do it" – the first isolating himself in his party by staging a "great sulk", the second actively plotting against her successor, helping to fuel the Tory party's civil war of the 1990s.

From the 18th century onwards, 14 prime ministers have staged a "comeback" and served in the governments of later administrations and under other prime ministers. In the 1930s, both Baldwin and MacDonald rotated in and out of the premiership in the "National Government" coalition, though it seems unlikely that David Cameron will favour this revolving door model in his own coalition government. Given the changes to the politics of party and leadership in recent decades, a further role in government seems unlikely for Brown.

Most ex-PMs have ended up in the House of Lords, which Tony Benn called "the British Outer Mongolia for retired politicians" and Asquith described as "like speaking by torchlight to corpses in a charnel-house". Being in the Lords does have the advantage of providing a platform for former prime ministers to air their views and contribute to political debate. Both Douglas-Home and Callaghan thrived in this "elder statesman" role. But modern ex-PMs, like Blair, can command media attention and make their voices heard whenever they want to without donning ermine robes.

Having already written several books and with a PhD in history, Brown will certainly be putting pen to paper. Although prime-ministerial memoirs are now almost obligatory, perhaps serious tomes on history and political ideas might be more to Brown's taste, following in the footsteps of Churchill who famously said "history will be kind to me

for I intend to write it". The majority of former 20th century prime ministers have told (and sold) their stories, usually for the purposes of detailed historical self-justification, settling of scores and making money. Tony Blair negotiated a deal worth 4.6m, for his memoirs (due out in September). He was not the first. Lloyd-George secured 90,000 from the Daily Telegraph for his memoirs, the equivalent of 3m today. In truth, prime ministerial memoirs are often dull and hard-going. Attlee admitted his were "not very good", while Wilson described his book, Final Term, on his 1974-76 premiership as "boring".

Until Tony Blair, former Labour premiers like Attlee, Wilson and Callaghan did not acquire money-spinning directorships or business appointments, as some of their Conservative counterparts did. Blair is estimated to have made at least 20m since leaving office, from his book deal, highly-paid advisory roles with JP Morgan and Citigroup, consultancy work for foreign governments and companies through "Tony Blair Associates", and huge fees on the international lecture circuit. He has "run Tony Blair as a business", according to one former Number 10 aide. John Major has successfully combined making money in private business with being active in a wide range of charities.

Brown has pointedly said that he will not seek lucrative business positions and would prefer to "make a difference" and "do something good" through charity or voluntary sector work. He has already foregone a substantial income by agreeing to reforms of the prime ministerial pension, but is unlikely to have to borrow from the Crown, as some

of his 18th and 19th century predecessors did.

Perhaps he will set up a charitable foundation-cum-personal think tank. As a former academic, offers of visiting chairs at prestigious US universities might be expected. Widely respected in the USA and on the world stage, there has also been speculation that he could be in the frame as the next head of the International Monetary Fund, a post that could become vacant next year.

He would certainly be the most high-profile and heavyweight figure to occupy that post, which has usually gone to former finance ministers or central bankers from European states.

Contemporary journalists regularly assert that British ex-prime ministers never go on to better things; their best times are behind them. They are wrong. There may not be a clear or established role for them, but Gordon Brown can be reassured that most have done plenty of worthwhile, interesting and significant things in the years after they have left Number 10.

Kevin Theakston is Professor of British Government at the University of Leeds and author of After Number 10: Former Prime Ministers in British Politics (Palgrave, 2010). His History & Policy paper, What next for Gordon Brown?, is published today at www.historyandpolicy.org.