Call it the Quantity Theory of Inanity. It would be wrong to say that Boris Johnson doesn’t still enjoy prime minister’s questions. Like any sociopathic narcissist he cannot resist being the centre of attention. The noise, the lights, the cameras. It’s one of the few ways Boris can tell he’s still alive. It’s just that the cracks are beginning to show. Even a few months ago, the cheers from the Tory backbenchers that greeted Johnson’s appearances in the Commons sounded almost sincere. Now they seem forced. Pavlovian responses from a bygone era. The Fool is now the fool, a fading music hall act reduced to babbling nonsense. A hollow man, bereft of redeeming qualities. As Boris shrinks, so Keir Starmer grows. There was a time when the Labour leader looked awkward at PMQs. He had all the right lines, but the delivery kept falling flat. His arrows mere paper darts that left Boris unharmed. He knew it, his MPs knew it, and the pretence that he was in his element was killing them both. Now, though, Keir has found his range. There is a confidence, a swagger to him. He is beginning to look and sound like a leader. He’s finally got the shadow cabinet he wanted and he’s not afraid to assert himself. Most of all he is comfortable in the job, because he knows he’s got Johnson’s measure. Boris no longer holds any terrors or mysteries for him. He’s just a third-rate chancer who always lets you down in the end. And, more often than not, in the beginning. Someone who can be picked off at will. For the last three PMQs, Starmer has effortlessly come off best by attacking Boris on matters of trust. Something that has never been the prime minister’s strong point. And this week the Labour leader was at it again. He started with the story the Daily Mirror had broken overnight about Boris breaking his government’s own lockdown rules by holding parties at No 10 last year. Didn’t this just show the prime minister was incapable of being taken seriously as someone who kept his word? Johnson did his best to look astonished. Though not so much that he denied the party had taken place. Rather he tried to make out that the party had never really been a party. It had just been a normal day’s work that had morphed into someone opening a few cases of champagne. Boris could make his own bubbles as he saw fit. A Westminster bubble. And Boris knew, it really had not been a Christmas party because, as far as he knew, no one had had sex with him. Which is his definition of a proper party. Keir was unimpressed. It had definitely been a party – there had been booze and games – yet Johnson was insisting it had taken place within the guidelines in force at the time. Both things could not be true. “It’s one rule for the prime minister and another for everyone else,” Starmer observed. Much like mask-wearing. Johnson had just about managed to strong-arm Jacob Rees-Mogg and Nadine Dorries, long-term mask refuseniks into reluctantly wearing face coverings, by telling them it would hide their lack of shame; but there were still at least 20 backbenchers boldly challenging the Omicron variant to do its worst. Though in their minds, they were the untouchables. Covid was something only the little people got. Having made plain there was little reason for the rest of the country to pay any attention to what the government said, as there was little chance it was listening to itself, Starmer moved on to a leaked report that not only showed most of the promised 40 new hospitals would amount to little more than a paint job in A&E but that the Treasury thought there was little chance of them ever happening. Outrageous, Boris exclaimed. In his own world every time a new lock is fixed to a toilet door a new hospital is built. It won’t be long before we find that the 40 hospitals are just the same hospital being built 40 times. “He drivels on irrelevantly,” Johnson said of Starmer, bouncing up and down nervously and waving his arms sporadically. Only it was Boris who was drivelling on irrelevantly. He had nothing to say. No defence. His MPs may have been willing to give him a bit of leeway but two years on they expected some delivery. Two Tory backbenchers dared to ask when their constituencies might receive some levelling up funds. Johnson laughed and all but admitted they wouldn’t be getting a penny as long as there were Labour councils in charge of the local authorities. The Tory benches went noticeably quiet. They can sense their leader is becoming a liability. The joke is no longer funny. Johnson has nothing left to offer but broken promises. The master of the profane, the maestro of the inane. A man incapable of leading by example. When the shit hits the fan he’s off partying with his mates. Someone who treats the country as mugs. And sooner or later the country will wise up and decide it’s had enough. John Crace and Zoe Williams will be live on stage in London at a Guardian Live event on 13 December. Join the conversation online by booking tickets here. A Farewell to Calm by John Crace (Guardian Faber, £9.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.