Once upon a time, Boris Johnson compared his opponents to a greased piglet first Tony Blair and then David Cameron before Cameron returned the compliment and applied the phrase to him. It certainly applied to him today. 
Keir Starmer had come to the Commons with a well prepared case for the prosecution, and tried to turn Prime Ministers Questions into a session of the public inquiry into the governments handling of coronavirus. It was a careful and serious approach that had no hope of confining its slippery, smooth-skinned quarry. 
Starmer and Johnson traded dates, warnings and levels of restrictions on social mixing to neither sides advantage. After four questions, the prime minister took refuge in the defence that Labour was still advocating for keeping schools open on the day that he announced the third lockdown. He then contradicted himself without a trace of embarrassment, saying of Starmer: Youd think he had no policy other than to plunge the country into 12 months of lockdown.