Cameron, Brown and the canoeist

Prime minister's questions sketch
By Nick Assinder
Political correspondent, BBC News website

Now here is an image to conjure with - Mr Bean (played by Gordon Brown) in a canoe, suffering from amnesia and up the creek without a paddle.

Mr Cameron hopes the prime minister is up the creek

If that doesn't give Rowan Atkinson something to work on for his next comic sketch then David Cameron and Vince Cable aren't the script writers they aspire to be.

This attempt to re-cast the serious prime minister from heavyweight figure into comic turn started last week, of course, when the Liberal Democrat leader branded him Mr Bean.

Oh, how David Cameron must have wished he had come up with that one in his bath.

He did his best this week with another assault on Mr Brown's integrity, competence and trustworthiness.

The killer question, however, was why on earth it was taking the prime minister so long to appoint a new sleaze watchdog to replace Sir Alistair Graham who was "let go" seven months ago.

Had not Mr Brown entered Downing Street pledging to restore trust in government, and wasn't this a sign he was failing to keep that promise?

Dodgy donations

With one of those astonishing coincidences, Mr Brown was able to announce the appointment was being made later this very day.

Mr Brown revealed sleaze buster appointment was imminent

Amazing how these things happen on just the right day. It is enough to make the most atheistic prime minister believe in divine intervention. Perhaps.

Still, this bit of good luck helped the prime minister a bit, as did the fact that the row over the dodgy donations is starting to lose momentum, for the time being.

But Mr Cameron wasn't quite finished. He moved onto what he claimed were broken prime ministerial promises on money for the armed forces, the position of "two jobs" defence secretary Des Browne, also Scottish secretary, and plans to only jail the number of offenders prisons can hold.

Whether he had always intended to sling these into the pot, or whether this was a bit of nimble footwork in the wake of Mr Brown's announcement on the sleaze watchdog was unclear.

But it was clear that, despite boisterous attempts by both sets of backbenches, the exchanges were running out of steam.

So Mr Cameron released his final shot: "He wants us to think he is like the man in the canoe - he hasn't been around for the past five years."

Mr Cameron believes the prime minister is indeed up some sort of creek and his job is to continue chucking rocks at his canoe.

But he also knows that, for the moment, it is the current that is carrying Mr Brown's boat - he just hopes it is towards a Niagara-style waterfall.