During Commons exchanges on Monday over lockdown parties in No 10, Boris Johnson said of Sir Keir Starmer: “(This) former Director of Public Prosecutions … spent most of his time prosecuting journalists and failing to prosecute Jimmy Savile, as far as I can make out.” What seemed to be a throwaway line uttered in the heat of the moment has become another stick with which to beat the Prime Minister. He has been accused, even by some of his own MPs, of smearing the reputation of Sir Keir “without evidence”. Indeed those two words accompany every news bulletin on the BBC in which this episode is referenced.

The implication is that Mr Johnson is repeating a calumny found on the internet in which the Labour leader is accused of personally blocking a prosecution of Savile. But it is clear that Mr Johnson was making a more general point about the responsibility that falls on the head of any organisation to answer for its actions. Labour is quick to accuse the Prime Minister of many breaches of the Covid regulations “without evidence” and are adamant that he must take overall responsibility for the activities of his officials whether or not he participated personally. They are right to do so. The old adage that “the buck stops here” still applies.

What is even more bizarre is that Sir Keir issued an apology in 2013 for the shortcomings “in the part played by the CPS in these cases.” This makes the “smear” charges levelled at Mr Johnson even harder to understand. The idea that the former DPP should escape any censure for the actions of the organisation he led, whether he was directly involved or not, is a novel departure from the concept of accountability.