As a former special adviser, Tom Clark of the Guardian knows a thing or two about the dynamics of the Labour leadership contest. And he is surely right that the key "headline" from last night's New Statesman debate, my report on which is here, was that Ed Miliband articulated a more leftist approach, thus creating "clear, cold" water between himself and his brother David Miliband.

Another key element of the story of last night was the extraordinary body language between the Milibands themselves, and between Ed Balls and the Milibands. But that is another tale, for another day.

To be fair to Ed Miliband, anyone who has known him for some years knows that his natural instincts are on what is known as the "soft left" and that, unlike some "Brownites" and, to an extent, unlike his brother, his politics are to the left of New Labour.

However, Clark goes on to suggest that last night Ed tacked left as a result of Diane Abbott's entry into the race. That may or may not be true. But if it is, as Clark points out, David Miliband should take some credit for the very grown-up way in which he ensured, through his own nomination and those of supporters, that Abbott got on the ballot paper.