The Sketch: Nuclear war, Tehran: there's a few years left in the PM

You do wonder what ministers are for. Whatever it is, it's not what we think. It can't be to manage departments - they don't have time before they move on. It's not to be responsible for things that happen (the Dr Demento doctrine relieves them of that burden). It's not to be a spokesman for departmental issues - the only category Rosie Winterton might fill (poor little poppet). In her fragrant case it doesn't matter - unless you fall under her care.

But what about Jack Straw? He was Foreign Secretary for a while and he must have been good at it. He was elliptically praised by the Prime Minister yesterday as being the reason the US started talking to Iran after decades. But at the height of his powers he was sacked to be replaced with the dismally mediocre Margaret Becket. "Fuck!" she said, on being appointed. As did we all, I suppose.

Ministerial appointments, we can deduce, have one underlying purpose: to secure the Prime Minister's position. And that produces a very unwelcome question: would a nuclear war in the Middle East help or hinder the PM's chances of staying in office for the next two years?

It's hard framing that question of such a nice man. Christian instincts, he won't pass by on the other side, you know. He really does want to make the world a better place. Has he considered the effect of a nuclear strike on his relationship with Gordon Brown? But of course he has. Why wouldn't he?

A nudge from Andrew Mackinlay clarified a line the PM will want to make more of. Iran is supplying arms to Hizbollah - and they bear a remarkable similarity to arms used by insurgents in Basra. The case is building.

"We have to understand why this began," he said. I'm not sure there's time. Some said it was the kidnap of the corporal, others said the 1,600 rockets fired by Hizbollah. Was it targeted assassinations? The Wall? The settlements, the suicide bombs, the rejection of the Clinton deal? Sir Peter Tapsell said it went back to 1967. But it goes back to Moses.

Two questions drew interesting answers. Julian Lewis: "Has the Prime Minister of Lebanon actually asked for our help? "Er... I think they are looking for help," the PM said. That is, "no". And from Patrick Cormack: As the PM said he was doing "everything he could", had he spoken to the President of Syria to lay down the law? Er... it wouldn't do any good.

Maybe he has cleared the way for war on Iran. Jack Straw was a vocal opponent. That's not what ministers are for.

sketch@simoncarr.co.uk