This Saturday Dolly Parton performs live at the Glastonbury Festival. Last weekend David Blunkett announced he was standing down as an MP. Both are 68 and in robust health. One rocks on seeking new career highs. The other concludes that the career highs are all in the past.

Dolly and David are part of a pattern. Celebrities are getting older. Big political figures are getting younger. Last weekend, on the day David explained why he was retiring as an MP, ITV broadcast a concert from earlier this year in which Paul McCartney mesmerised an American audience.

McCartney is 72 and will be touring in the US later this summer. Clint Eastwood is currently publicising the first film musical he has directed. He’s 84. At almost 80, Woody Allen is contemplating returning to stand-up comedy. In the UK there are many equivalent figure. Bruce Forsyth is performing energetic one-man shows this summer. Some of the best broadcasters - Melvyn Bragg and John Humphrys spring to mind – are in their seventies.

In most fields people have to work longer or are choosing to do so. But in politics the reverse applies. The young and inexperienced rise to the top very quickly. The experienced ones depart the scene. Both Tony Blair and David Cameron became youthful Prime Ministers with no previous experience of power.

Gordon Brown and George Osborne were young Chancellors, similarly inexperienced. When Nick Clegg became Deputy Prime Minister in daunting circumstances he had been an MP for a single parliament. In all cases the inexperience showed.

Recent leadership contests have also tended to be youthful affairs. A young William Hague won the Tory leadership in 1997 when he was not ready for the its impossible challenges. When Labour held its leadership contest in 2010, veterans such as Alan Johnson, Alistair Darling, David Blunkett and Jack Straw – all of them still in good health and good political form – were absent.

That was in marked contrast to Labour’s leadership contest in 1976 when the candidates were all in their fifties and sixties, fully formed politically after years of cabinet experience and a thousand internal party battles played out on the bright lights of the political stage.

The heavyweight charismatic candidates then – Jim Callaghan, Michael Foot, Tony Crosland, Roy Jenkins, Tony Benn and Denis Healey – all had their flaws but no one could have accused them of lacking political experience.

Part of the explanation for the early departures in the current era is the freakishly long periods of one-party rule since 1979. By 1997 senior Tories were exhausted after 18 years in power or had lost their seats. The same applied to Labour in 2010 after 13 years of unbroken rule.

But there are other factors too. There is no longer a sense of orthodox politics as a vocation for life. That sense is replaced by an assumption that politics is a young person’s profession. After the Conservative government was removed in 1974, all its key figures stayed on to fight the battles of opposition. When Labour lost in 1979, the big, charismatic personalities also remained for the years of impotent hell that followed. In contrast, look around now and a lot of seemingly formidable figures from the last two decades are in the private sector or on television.

The generational issue is complex. Of course there is a need for parties to move on. If ministerial veterans had stood for the leadership in 2010 there would have been a mountain of hostile columns and tweets screaming that Labour needed to break with its past. Parties need youthful figures close to the top to bring fresh approaches and to symbolise new beginnings.

But politics is also an art form where the classiest artists learn from direct, personal experience. Those who have been exposed to raging heat on the political stage are better placed to act when then the temperature next reaches boiling point. When plunged into crisis in government Blair, Brown, Cameron, Clegg and co could not ask a valuable question: What did we do last time? There was no last time.

Ed Miliband is fortunate in that his shadow cabinet still includes figures who have been exposed to the heat, who have experience of government and opposition. He needs to make the most of them in the final grinding months before the election, and make use of them in power if he were to win. There need to be a few at least who are able to answer the question: What did we do in the last crisis?

As Paul McCartney explained when asked how he could still perform live for three hours: “That’s what I’ve always done. In Hamburg the Beatles performed for eight hours sometimes”. His past is a guide to the present.

While Dolly rocks and Melvyn presents a thousand TV and radio programmes most politicians peak in their thirties and forties. We need a few more Dollys in politics.

Cameron is not fair game for volley of criticism

The current political battle is similar to a close match at Wimbledon. The critical focus is on one player and then the opponent makes an error and unrelenting attention moves to the other side of the court. If David Cameron fails in his bid to prevent Jean-Claude Juncker from becoming the next EU president, parts of the Conservative party will have a mini-nervous collapse.

For a time the attention would move from Miliband’s problems to Cameron’s. Unfairly, the Prime Minister has been criticised for noisily seeking to veto Junker, as if there were a quieter route towards such an outcome. Once Cameron had decided to seek a veto he had no choice but to speak out publicly. Having made a public declaration there was bound to be a lot of noise.

Cameron is not to blame for the way he has sought to block Juncker or for the likely failure of his attempt. But it is an early indication of the degree to which he is trapped by Europe. Imagine what it would be like if he were to win the election by a tiny majority. He would head to Berlin and other European capitals for an even more demanding negotiation. The outcome would almost certainly not satisfy a significant section of his party. At which point there would be more than a mini-nervous collapse.

All three main parties are extremely fragile at the moment but because of Europe the Conservatives remain in the most precarious position of all.