Watching Jeremy Hunt's day at the Leveson inquiry, one thought hit me like a hammer: that he looked like the perfect modern politician, and for all the wrong reasons. He seemed shaky, inexperienced and regularly out of his depth. In an office reception, I briefly watched his cross-examination with the sound turned down and, strangely, those qualities were even clearer. Really, what kind of senior minister – tipped for the Tory leadership, to boot – would not understand the meaning of quasi-judicial, or the need to minute all official meetings? Didn't those text messages have a kind of boy-man, David Brent-ish ring to them? Anyone resident in the real world would probably not leave him in charge of a barbecue, let alone a ministry.

Yet this is where politics and power have ended up: in the hands of too many people – men, by and large – who style themselves as expert players of the game, but know far too little about the political fundamentals (Hunt's backstory, involving time in Japan and a successful education business, might seem to set him apart, but he looks and sounds like a risen-without-trace politician straight from central casting).

The prime minister apparently has a poor eye for detail, a weakness for iPad games and no clear idea of where his administration ought to be headed. The Treasury is commanded by George Osborne and Danny Alexander, and look what has happened – not just an economic plan that is failing, but the most abject budget in living memory.

With the addition of Nick Clegg, the average age of the "quad" they make up is 42.75. The Labour frontbench has much the same age profile – indeed, since Ed Miliband began reshuffling his team, the sense of untested youth has only grown greater (witness the 35-year gap between Vince Cable and his shadow, Chuka Umunna). To be fair, Miliband's choice of greybeards is rather limited by the massed exit of big Labour figures after 13 long years of government, their often damaged reputations, and his need to define his leadership in terms of fresh approaches. But note one recent development – the promotion of Jon Cruddas, whose singular contribution to Labour politics is down not just to being an iconoclastic free-thinker, but the insights of a politician with a rich hinterland, who has just turned 50.

How did all this happen? Part of the explanation is traceable to the cult of that other Leveson star Tony Blair, and a fatal modern mistake: seizing on the occasions when relative youth has symbolised a necessary changing of the guard (Blair in 1997, Bill Clinton in 1992), and thinking that therein lies a dependable formula for every political occasion. A lot of blame lies in the woeful modern career path – university, followed by life first as a researcher, then special adviser, a seat in your early-to-mid 30s and, if you're lucky, a big role not long after.

But there are other explanations. Cultural historian Alwyn Turner argues in his book Things Can Only Get Bitter that Labour's hope-crushing defeat in 1992 pushed a whole generation away from politics, leaving a huge age gap. Such big hitters as Blair, Brown, Mandelson and Darling were born between 1945 and 1954, and the generation led by the Milibands and Ed Balls all have birth dates no earlier than 1965. Look for anyone born between 1955 and 1964 and you encounter slim pickings. From Labour's last spell in government, Turner cites only Jacqui Smith. Though a bit better off for fiftysomethings, the Tories have their own version of the same story, presumably traceable to the toxic reputation of Major's government.

Stewardship in troubled times requires more than a smattering of grey hairs. At the height of Britain's travails in the 1970s, Denis Healey was in his late 50s; when she began pushing her box-fresh project down the nation's throat, Margaret Thatcher was 53. Clement Attlee became PM at 62, and his first two chancellors took office aged only four years younger. And take note: the most successful modern British politician is Alex Salmond, who is 58 this year. François Hollande is the same age. As loth as I am to write a single sentence about this weekend's mad parade, maybe the enthusiastic celebration of the diamond jubilee underlines an associated point, that somewhere in most people's minds, wired in since human beings came down from the trees, is an innate understanding of age and experience, and their infinite uses.

Even if there is not much they can do about it, some of the most clued-up politicians seem to agree. When Ken Clarke returned to frontline politics, I wrote an article suggesting that such battle-scarred figures were exactly what times of crisis often require. I was emailed by a shadow Tory minister of roughly my own age, who agreed with most of what I had said, and invited me to the Commons for wine and crisps. He's now in the cabinet. We talked, as I recall, about what a turbulent time his party was bound to have in government, and the contrasting experiences of our generation and those that had preceded us.

Our mid-20s were defined by such touchstones as the European Championship of 1996, Blair, and Oasis; at much the same age, Denis Healey was a landing officer at the battle of Anzio, and Edward Heath was fighting in Belgium, the Netherlands and Germany. Would that their generation could be called on today, when Europe and the wider world are once again full of grave threats, but the greenhorns in power are fixed in our minds as mere dilettantes, breaking from their duties to either fire off silly texts, or play Fruit Ninja.

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