So, how does Labour win – and win big – in London?
We already have a clear idea, from commentators and the new Mayor himself.
The simple answer: talk to voters about what they want to talk about, in terms and tones that they want to hear.
Sadiq Khan and his excellent team did this in spades over the course of the campaign, and deserved to overcome a thoroughly nasty and divisive Lynton Crosby campaign, which – for once – did failed to deliver for the Tories.
As a result, Labour now has a big opportunity in the capital, to deliver a rightly ambitious programme for building affordable housing, freezing transport fares and restoring community policing across the capital.
But Sadiq built up a platform which was far more than the sum of those individual policy parts.
He committed to be the most pro-business Mayor the capital has had, understanding that failing to engage with the reality that the people in the capital work in the private sector – the vast majority in SMEs –would sound like he didn’t understand London’s economy or Londoners’ working lives.
He took a clear position on the EU referendum. He knew that for London’s future Mayor to do anything other than campaign for Remain would risk London’s status as a world city. His position also spoke to the hundreds of thousands of EU citizens living in London. Ironically they have no vote in the referendum; so they used this election to vote for a candidate who would protect their interests.
Sadiq vowed that safeguarding London from terror would be his top priority. He took a clear and consistent line on tackling extremism, worrying that introspection and isolation provided too easy a road to radicalisation for some young Muslims.
And he showed strong leadership on the issue of anti-Semitism. Keen observers would realise this was consistent with his strong track record of reaching out to the Jewish community, rather than a political opportunity exploited. But it has an impact which went beyond Jewish Londoners; in speaking to Londoners of all faiths and none that he had no truck with what is perhaps the oldest hate of all.
He underlined his determination to be a Mayor for all Londoners in this way, and also in the way he campaigned across the capital, regarding (and winning) votes in Croydon and Hillingdon as important as those in Camden and Southwark. There were no no-go zones – and, as a London Assembly candidate, my worn-through shoe leather is testament to his resolve and energy in a campaign which zig-zagged across all 32 boroughs.
He won because of all this and more, packaged and delivered professionally, and with a fervent commitment to repetition which ensured there Londoners knew who he was and what his priorities were.
So now, he has two mandates. The first, most importantly, is the handsomely-won authority to run London Government.
But he also has the authority, and responsibility, to speak to the rest of the Labour movement about winning, and winning well.
When he writes that “Labour has to be a big tent that appeals to everyone – not just its own activists”, we should listen.
When he talks to the aspiring entrepreneur, as well as the nurse or the tube driver, we should listen.
When he promises to root out extremism and antisemitism, and regard protecting London’s streets from terrorism as his number one concern, we should listen.
When he engages with all voters, rather than chiding or ignoring those who aren’t lifelong Labour supporters, we should listen
Although he certainly didn’t run for office on this basis, the fact is that many Labour members and supporters, across the country, who are more interested in winning power to do good than the heroic failure that may come as a consequence of ideological purity, will follow Sadiq’s example.
The Tories are tearing themselves apart over Europe, alienating swathes of middle England on the NHS and junior doctors and are ditching major school reform. They are there for the taking, as we did in London.
For the sake of the people who need Labour in power across the whole country, rather than pontificating, we need to listen to the bus driver’s son.
Mike Katz was a London Assembly list candidate. He tweets at @mikekatz