One of the oddest ideas in UK politics is that Labour chose ‘the wrong brother’. Surely the very idea that we had to choose between two sons of the same grandee and, oh, by the way, the Labour leadership was really the birthright of the eldest in any case, is absurd at every level.

The simple fact is that the seeds of Labour’s crushing defeat this week were sown when the Blair and Brown camps killed all of each others political heavyweights and replaced them universally with creatures of extreme patronage – special advisors to a man and woman – who were never tested as MPs to see if they were truly any good at politics off their own bat.

It’s often said that David Miliband was defeated by the unions, but this is to see that leadership election through a distorted lens. From the very start, it was assumed that the unions would be against him – yet it was also widely accepted that he was miles ahead in the race. His team’s gameplan was simply to stay ahead by keeping the lion’s share of the MPs and general membership vote. But over the weeks, he steadily lost that lead because he just couldn’t engage with MPs. When Ed turned out to be much better at chatting to people in corridors, David’s team started to panic. They resorted to threats – ‘you’ll never be in his government if you don’t support him’ – and reminders that he was Tony Blair’s chosen man.

The harsh reality, though, was first that the mood during the leadership contest was low and few really thought we could win in 2015, so government jobs didn’t feel like a serious option anyway. Second, everyone knew that until all the serious Blairite contenders were  killed off (Byers, Mllburn, Reid, Hutton and the rest) the idea that Blair regarded David Miliband as his successor was risible. Simply being Tony Blair’s last-ditch option was never going to be enough to help David Miliband to victory.

Most people who know the brothers know that they’re peas in a pod as far as being oddball geeks is concerned, and that Ed has the huge saving grace of being charming with individuals and small groups. I remember it was impossible to walk down a corridor without being grabbed by Ed for a chat. Whereas many MPs were at first puzzled then eventually troubled by receiving calls from ‘members of David’s campaign’ – based half-a-mile from Westminster – while David seemed unable to sell his candidature to them personally. David lost his huge lead not because of the unions – he lost it, and the vote, because he just isn’t very good at talking to people or expressing himself plausibly one-to-one without using silly black-box, wonk-type language.

David and Ed were not, of course, the sole expression of the new special-adviser aristocracy in the Labour Party. Indeed, with only rare exceptions, virtually every senior member of the shadow cabinet came out of what became a virtual policy of nepotism. Whereas Blair, Brown and most of their senior ministers had risen through their own mastery of the political arts – including the dark ones – the post Blair and Brown Labour Party yielded to a new aristocracy of former special advisers. And here is the terrible truth – they were exceptional backroom folk but simply weren’t much good at being ‘principals’. Under them, Labour hasn’t won a single major political election. Under their influence in cabinet then leadership in opposition, Labour lost both UK elections, both London mayoral elections and both Scottish elections – indeed Labour’s now been more or less wiped out in Scotland altogether and may well cease to exist in its coming form in the months to come.

The saddest thing about that Scottish wipe-out was that the 2010 intake from Labour in Scotland was of a strikingly high standard and none of them at all came from the ‘Labour aristocracy’ background. The Greg McClymonts, Willie Bains, Pamela Nashes. Indeed, the Scottish intake had this in common with many of the 2010 intake form England and Wales. What was noticeable, though, was that all such folk – with the exception of Chuka Umunna, were kept in the second rank of the shadow government, displaced by the special-adviser aristocracy in the shadow cabinet for no reason other than simple nepotism and metaphorical secret handshakes.

As Labour chooses a new leader, it must behead its failed old aristocracy and find a leader wo entered in the 2010 parliament (who will have been in parliament by up to 10 years by the next election) who has made themselves. This is not to say that no former special advisers at all need apply – Liz Kendall is obviously someone who fits the bill in every sense and she’s manifestly done that for herself – it’s to say that Labour has to pick a leader on the basis of personal traits and wide public appeal, not on the basis of being part of the in-crowd.

Dan Jarvis? Stella Creasy? Chuka Umunna? Sarah Champion? Steve Rotherham? There are other truly gifted, smart and appealing folk from the 2010 intake untouched by the horrors of the years of the failure of the aristocrats. If one of them gets a chance because Labour’s truly serious about finding the right leader, Labour could win in 2020. If the door stays open to aristocrats-only then Labour’s screwed for many years.