Sir Keir Starmer begins to look more and more like a crash-test dummy, sitting expressionless, tilted to one side, in the wreckage of a driverless car which has madly steered into a tree with him on board but not in charge. He also looks less and less like the chief minister of a nuclear power and a major economy.

Nobody, he insists, told him that Peter Mandelson had failed his vetting procedure. And so he appointed him to the position of HM Ambassador to Washington DC, one of the most sensitive and influential posts in his gift.

The whole point of being PM is to be in charge.

No other job is so powerful. The person who holds it can summon whoever he likes to his presence and demand the facts. He can issue instructions which will, in almost all cases, be obeyed.

This is all most gratifying to the holder of the office – but it comes with a price. He really cannot then say that he did not know what was going on.

A bitter joke is circulating in Westminster and Whitehall that the Premier can at least now solve the small-boats crisis by renaming the English Channel 'Keir Starmer's Desk'. For, after that, nothing will ever be able to get across it.

It is also more than a little ridiculous that this man, so bizarrely ill-informed about his own Government's most exalted and secure activities, once pilloried Boris Johnson over a so-called party at No 10 Downing Street during the Covid lockdown.

Sir Keir then accused Mr Johnson of 'months of deceit and deception' and led calls for him to 'do the decent thing and resign'.

Sir Keir also described Mr Johnson's defence – that he did not realise the event was a party – as 'so ridiculous that it is actually offensive to the British public'.

On another occasion he jeered: 'Look, there are only two possible explanations: either he's trashing the ministerial code or he's claiming he was repeatedly lied to by his own advisers and didn't know what was going on in his own house and his own office. Come off it.'

Well, like many people who have been piously censorious in his time, he now finds his own righteousness coming back to bite him. He should come off it.

It is extraordinary how his carefully assembled and polished image of being the Great Prosecutor has become tarnished and dented.

Far from being fully on top of events, forensically probing the machinery of government with brilliantly researched questions, he is resorting to the feeblest defence of the embarrassed leader. 'Nobody told me.'

The coming week may contain even more of this sort of drama, with others also saying they didn't know what was going on.

Given Whitehall's immense skill in concealing its right hand from its left hand, and given the fundamental crisis in the Labour Party, we may never get to the bottom of this.

But until it is resolved, the people of this country are entitled to wonder whether the Prime Minister is actually in charge of the government he heads.

And if he isn't, we must all hope that the coming local and devolved elections will at least resolve that problem.