Labour’s hopes for a smooth and confident launch of new leader Ed Miliband have been thrown into turmoil after remarks made by brother David during Ed’s inaugural speech became the main story — and fervent speculation that Mili-D will announce his departure from politics tomorrow.

The remark came midway through the speech, as Mili-E was expanding on Iraq and his opposition to the war (or claimed opposition — he wasn’t an MP in 2003, and there ain’t much on the record) — although nobody heard it at the time, as it passed silently between Mili-D and deputy leader Harriet Harman.

Mili-E’s statements that the war was wrong, was based on falsehoods, and generally the sort of thing Labour shouldn’t do (except Afghanistan, of course, which remains the good war) was greeted with applause throughout the hall, except at the very centre, where old New Labour was gathered.

At that point, the cameras had all trained on the remaining pro-war folk — Mili-D, Harman, Jack Straw — who were sitting in stony silence. It was a much-anticipated highlight of the afternoon — indeed Politics Show host Andrew Neil had gleefully told dismayed Labour grandees beforehand that it was the moment he was most looking forward to.

Mili-E’s speech sailed on pleasantly enough — get back to Labour basics, listen to people on immigration worries, go in hard against the banks, living wage — and it was genuinely judged a dutiful if unexciting effort.

But by late afternoon news channels had had lip readers decipher Mili-D’s remark to Harman, which turned out to be “why are you clapping when you supported the bloody war?” To which Harman replied, in true New Labour fashion, “cos he’s the leader and I support him”.

The remark, hardly a killer gaffe, became a lighting rod for renewed speculation about whether the brothers could ever find a stable modus operandi, and threw a shadow over the whole thing.

With David Miliband still having failed to accept Mili-E’s offer of Chancellorship, the smart money is that he’ll now f-ck off. Indeed, he has already left the conference early, and returned from Manchester to London, a pretty decisive gesture.

The conference, trying to get away from the traditional red, has had its stages and public areas bathed in a deep mauve all week long. It’s meant to suggest a combination of red and blue. Instead, it made the whole thing look truly Roman, a struggling empire bathed in imperial purple, and everyone’s relatives lying dead on the floor.