Donald Macintyre's Sketch: Fairytale of New York is a comfort to delegates

There’s a good line in the film City Hall when, just before a press conference, John Cusack tells the New York mayor, played by Al Pacino: “You look good.”

“Of course,” says Pacino. “I’m the mayor.”

And today Bill De Blasio, the Labour conference’s starry guest speaker, Pacino’s real life successor and the first Democrat mayor of New York since 1993, looked good too. A big man in a yellow tie, who effusively man-hugged Ed Miliband before and after his speech. A man with actual power. A man the pundits doubted but who found himself “not just winning but winning big on election day”. Unsurprisingly, he got a standing ovation before and after his speech.

Whether his script, or at least the ad libs, was quite up to Hollywood standards, is more doubtful.

True, he made the audience chuckle with his complaint that all the advertising misspelt “Labor” by giving it a redundant ‘u’. He coined a great word never before heard on British soil – “undergird” as in “undergirding the foundations of success” – so much more macho than the wimpy “underpin”.

And while some of his rhetoric was distinctly transatlantic (on hard-pressed working families, for example, “the tired eyes of a waitress whose second job is preceded by a second shift at her first… the shaky hand of the bus driver signing the paperwork for a payday loan”), it struck home nonetheless.

But when he improvised, he also lengthened. Labour’s message was not only “tangible and meaningful” but “substantive and real”.

He compensated by leaving out paragraphs of his printed text. This may have been in generous solidarity with Ed Miliband’s unintentional omission of any reference to the deficit on Tuesday, of course. But it also meant that while effusively praising the Labour leader he forgot to say the lines about him being the next and “great” Prime Minister.

It didn’t matter. He spoke the conference’s language and he had done his homework. Later, Harriet Harman (in one of her better jokes, describing Gordon Brown as having made “the biggest comeback since Cheryl Cole made it back into The X Factor”) had said how an American visitor to a food bank had asked “Does your government run this”, and had been told: “No – our government caused this.”

De Blasio didn’t make that mistake. He praised Labour’s policies on the NHS, on energy prices, and on childcare. He condemned the idea of “trickle down” wealth as “voodoo economics”.

He was applauded loudly for dismissing the idea you couldn’t have “economic fairness” as well as balancing the budget. And having come from a campaign launch on a cold January day in Brooklyn “with a few hundred people”, he had made it. He had won something and from the left. That was enough.