Crucial to the Ed Miliband camp’s narrative was the idea that the YouGov poll in early September – which for the first time put him ahead of David, albeit by only 51:49 – gave him the psychological edge. The theory was that ambitious MPs in the elder brother’s camp would jump ship in order to win promotion, as we reported at the time.

This was wrong. Ultimately only one MP quit the David Miliband camp in the last week or two: Chris Evans, MP for Islwyn. And even then it was not to join the Mili-E bandwaggon: he decided to back Ed Balls, whose political reputation – if not his campaign – had been picking up.

Perhaps politicians are rather less principled than some might think. Or they were restrained by the knowledge that hacks such as myself would be poring through sheets of paper (from this website) trying to spot the “turncoats”?

Sorry for the delay – have been writing for the main ft.com site, where we have written about the victory of Ed Miliband over David Miliband by the thinnest of margins.

The headline victory is astonishingly close, 50.65 per cent to 49.35 per cent.

More worrying for Ed’s team, as they snap open the champagne bottles (or ale, or whatever “New” New Labour drinks) is that he only beat his brother in one of three categories; the unions.

For unions and affiliates he picked up 19.9 per cent against 13.4 per cent for David. But David won by 17.8 per cent to 15.5 per cent for MPs and 18.1 per cent to 15.2 per cent for ordinary members.

That makes Ed an obvious target for those – the Tories, obviously – who want to portray him as “captured” by the union movement. The Ed team had been briefing this week that they thought they had won a majority of the ordinary members; it’s rather bad news for them that they did not.

I first revealed a few weeks ago that Unite had got around the Ray Collins (Labour general secretary) ban on putting pro-Ed Miliband literature in the same envelope as the ballot papers sent to its members. It had just put the envelope inside a separate envelope; simples.

As I wrote at the time:

At the start of the contest there was a row between Unite the Union and the Labour leadership because the former wanted to send out an envelope with its endorsement alongside the ballot papers. They were prevented by the party general secretary.

But what transpired was this; Unite sent out a big envelope containing its Ed Miliband endorsement with the voting papers in a separate envelope within. In other words, the leaflet backing Mili-E was the first thing that members saw when the mail arrived.

On Wednesday I revealed in FT Notebook that union officials had gone one further – to the anger of David Miliband supporters – and actually put Ed’s picture on some of the outer envelopes.

A politics professor has told the Guardian that this may not be in the spirit of the rules. He may or may not be right. In my opinion, it may be insulting to union members’ intelligence to suggest that this alone would govern how they vote. But if Ed wins, there’s no doubt that the Tories will use this to help fashion a narrative that is not exactly favourable to him.

At the start of the week I explained that I was having trouble laying off my 7:1 bet on Ed Miliband because the bookies were obstinately keeping David as the clear favourite. That has now changed, and I’ll be placing a bet on the elder brother at 7/4 (Paddy Power) in order to secure a profit.

David is still expected to win the first round of voting today, with strong backing from MPs and activists if not union members. Yet Left Foot Forward, the left-wing political blog, is predicting that the younger brother would edge ahead by a single percentage point with the help of second preference votes.

And Mili-E is now the out-and-out bookies’ favourite. This is despite opinion polls suggesting that he lacks his brother’s public appeal. Only 8 per cent of voters consider Ed the best person to lead the Labour party, according to YouGov earlier this month. A separate poll this month by ComRes, this time of Labour voters, found that he was the preferred candidate of just 11 per cent.

David Miliband was the outright favourite in both cases at 20 per cent and 26 per cent respectively, although nearly half of the public and Labour voters ticked the “don’t know” box. Andrew Hawkins, head of ComRes, tells me that his research showed that Labour voters believed that David was more likely to get Labour into 10 Downing Street than Ed – by 36 per cent to 10 per cent:

“On every measure which we tested, David Miliband was ahead of his brother by at least 50 per cent…Then again, electability doesn’t always come into it when Labour choose a new leader.”