Some years ago, at an African Union conference in Addis Ababa, I heard the then UN secretary general, Kofi Annan, say to an audience stuffed with life presidents: “One of the tests of leadership is knowing when to leave the stage.” All the big offenders were present – Robert Mugabe from Zimbabwe, Omar Bongo from Gabon, Teodoro Obiang from Equatorial Guinea and Yoweri Museveni from Uganda. They sat stony-faced amid much nervous foot-shuffling and laughter as the chairman, the former president of Mozambique, Joaquim Chissano (one of the few African leaders who stood down when his time was up), pointed at them and said, “And we all know who Kofi was talking about, don’t we?” It was an electric moment. Annan may have been talking about African presidents, but today his words might equally apply elsewhere. Is it not extraordinary that, more than 200 years after it was founded, a political system as open and allegedly sophisticated as that in the US can only offer the American electorate a choice between two elderly males – one a serial liar and the other a decent man well past his sell-by date. One can understand what drives Donald Trump (77) – a desire to stay out of prison – but why on earth should Joe Biden (80), who has held elected office since 1972, want to cling to power? And not just Biden; what of Nancy Pelosi (83), until recently House speaker, or the Senate Republican leader, Mitch McConnell (81), both visibly fading? Or, indeed, the revered supreme court justice, Ruth Bader Ginsburg, whose refusal to recognise that her time was up arguably gifted control of the most important institution in the US to the hard right when she died in post in 2020 at the age of 87. Despots at least have the excuse that, having trampled their enemies and made themselves rich beyond the dreams of avarice, they can’t guarantee that were they to relinquish the reins of office, they wouldn’t be called to account for their misdeeds. Political leaders in a mature democracy, however, have no such excuse. A comfortable retirement awaits them – a good pension, lucrative memoirs and (should they want it) adulation on the after-dinner speaking circuit. In the UK, whatever our problems, rule by geriatrics is not an issue, although once upon a time it was. William Gladstone, Winston Churchill and Clement Attlee – great men in their heyday – overstayed their welcome. Margaret Thatcher and Tony Blair, though by no means geriatric, had to be prised out of office. Some of our judges, too – notably Lord Denning – overstayed. Our problem, however, is almost the opposite: in the increasingly febrile UK, such is the pressure on a reigning prime minister that, in recent years, it has been rare to last a single full term, never mind two. And as for ministers, the turnover is extraordinary. Rory Stewart, to name but one, held five posts in four years. We could do with a bit more stability, not less. Many of the current generation of MPs seem to get their feet on the ladder when they are far too young. Some are not long out of university or a political thinktank. I am occasionally asked by an ambitious young person for my thoughts on how to get into parliament. My advice is always the same: “Go away and do something else first and then you might be of more use if and when you do get elected.” For better or worse, I was 39 when I was first elected as an MP. Experience in other fields is important. There is more to politics than tweeting. (Though I read with horror the other day that there are now companies that, for an appropriate fee, offer a bespoke social media service to young professionals vying for selection as candidates for parliament. Lord, save us.) Power, of course, when finally achieved, is addictive. Having striven for so long to reach the top – nearly 50 years in Biden’s case – there is understandably a reluctance to relinquish office. The longer you are in power, the more messianic you become. “All prime ministers go mad after two terms,” one of Blair’s closest advisers once remarked to me, only half-jokingly. The US system, for all its faults, does have one great strength: two terms and you are out. As for me, who only ever inhabited the political foothills, I stood down at the age of 62. As those who have read my diaries will know, a great deal of agonising preceded the decision. At the time I regarded it as either the best or the worst decision of my life. Thirteen years on, I am pleased to report that it has worked out better than I could ever have anticipated. It’s always better to go when people are still asking “why” rather than “when”. Chris Mullin is a former Labour minister. His most recent diaries, Didn’t You Use to Be Chris Mullin?, are published by Biteback