“We are in roughly the same position, my fellow global leaders, as James Bond.” Boris Johnson was addressing the climate summit in Glasgow (or, if you’re American, Edinburgh). But in what way did their situation resemble that of Ian Fleming’s secret agent? Are they bedding women 20 years their junior? Smashing things up without a thought to the consequences?

Well, possibly. But as it turns out he meant “strapped to a doomsday device, desperately trying to work out which coloured wire to pull to turn it off while a red digital clock ticks down remorselessly to a detonation that will end human life as we know it.”

When you meet a man who talks a lot about James Bond, the crucial thing to establish is which actor was playing the role when they were age ten.

Johnson is a product of the Roger Moore era. Moore played Bond for laughs, his raised eyebrow reminding us that he knew all this was ridiculous. This is very much the way in which Johnson plays the role of prime minister. Indeed, it is the secret of his success. It’s hard to criticise someone for not taking things seriously when they work so hard to advertise the fact.

Unfortunately, his speech was supposed to be a serious one, a call to action that would shift his audience from complacency and make them lift their eyes from their own troubles to focus of the larger threat. It was a message for Daniel Craig or Timothy Dalton to deliver.

“We know what the scientists tell us and we have learned not to ignore them,” Johnson went on, a line that lends weight to the theory that the prime minister’s speechwriters have a running bet on who can get him to deliver the most self-undermining line.

“I was there in Paris six years ago when we agreed to net zero and to try to restrain the rise in the temperature of the planet,” he said. Perhaps due to pressure of time, he didn’t mention that a couple of weeks later he’d dashed off a column for the Daily Telegraph arguing that those present “were driven by a primitive fear” which was “without foundation”.

In those days, Johnson’s chief scientific adviser seems to have been Piers Corbyn — yes, that Piers Corbyn — describing him as a man who “seems to get it right about 85 per cent of the time”. It’s possible that this estimate has since been revised downwards.

Still, when Johnson’s wife changes, he changes his mind. He now believes in man-made climate change. He made the case for engaging with it and doing more. But any speech whose recurring theme is James Bond trying to decide which wire to cut is always going to be a frivolous one.

When Johnson’s wife changes, he changes his mind

It wasn’t the worst of the afternoon. That prize goes to Joe Biden, as wooden and stumbling as ever. Has the US elected a worse orator in the last 50 years? He peered at his speech on the autocue as though it was the first time he’d seen it and delivered it with all the expression and eloquence of a reluctant 10-year-old forced to take a turn reading Oliver Twist to the class. He pronounced “Glasgow” as though he had never heard the word spoken out loud. Still, he was there, and he wasn’t yelling abuse at the audience, or telling them that climate change was a hoax, so he remains an improvement on his predecessor.

But Johnson’s funny speeches generally work because the audience expects them to be funny. It’s always interesting to watch him working a crowd that doesn’t get the joke. The delegates sat stony faced. The Trade Secretary, Anne-Marie Trevelyan, typed something into her phone. “We aren’t getting hotter, global warming isn’t actually happening,” possibly, or “clear evidence that the ice caps aren’t melting after all, to counter those doom-mongers.”

Johnson ploughed on. There was the obligatory reference to a Churchill speech. There were side gags that would usually have got a chortle — the suggestion he might still be prime minister in 40 years — but which were met with nothing. A slight panic appeared in the prime minister’s eyes.

“We may not feel much like James Bond,” he said, as he wound up. “Not all of us necessarily look like James Bond.” Silence. “But we have the opportunity, the duty, to make this summit the moment when humanity finally began — and I stress began — to defuse that bomb.”

In another context — a “comically polemical” newspaper column, say — it was an OK line, but it was an odd one to be deployed by someone under fire for not taking the summit seriously.

Roger Moore summed up his approach to acting as “get up early, say your lines, and not trip over the furniture”. Slightly greater efforts may be required if Johnson is to make a success of this week.