The Sketch: Honestly, the things you have to know to be the Prime Minister

Two hours and more in front of the Liaison Committee. It's often called a grilling but at best the Prime Minister is lightly poached and at worst coddled.

The MPs covered various subjects, occasionally sought a piece of information, often tried to catch him out, and generally set about him in a way that suggested he was a bit of a newcomer. There they behaved a little beyond what their status really permits. Somehow they'll be punished for that.

But did they get him to say anything new? Did they find anything out? Did they achieve their deepest purpose – to make themselves more attractive and popular to a wider audience?

If the wider audience admires long, content-filled questions demonstrating how much they know about their special subject, then their stock will have risen dramatically.

But honestly, the things you have to know as PM. He was asked how the withdrawal of the educational maintenance allowance would overlap with the introduction of the discretionary learner fund. Imagine being asked to answer that.

And if you knew it, you wouldn't know how the 30th percentile rule and the single room rate extension contributes to mixed communities, would you?

And then he's asked to ensure the survival of peat production in Yorkshire and the level of policing in Manchester, and reducing barriers to the Harriers on the carriers and the farriers for the marriers in the Palace – the range required of our leaders is amazing.

They all had it, certainly Tony Blair and Gordon. But those two – highly professional – predecessors had a psychological flaw which the amateur Cameron does not.

They had a foible of omniscience. They had to be seen to know everything – and were incapable of admitting they had been mistaken about anything.

Cameron, through some sort of ancestral confidence, is able to withdraw assertions quite comfortably. He doesn't have to bend the entire world out of shape to accommodate his error.

Thus, Cameron explained the Water Bill won't be delayed because the Queen's Speech needs to be in cycle with the election dates – and then he said: "That may be an excuse I've just given you, it's possible they haven't finished writing it yet, I'll go and check with officials."

And considering the data prime ministers are expected to master, the ability to deal with error is essential to keeping yourself sane. Still, it's early yet.

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