The choice facing Labour that could define Starmer's government

Reform UK's victory lap came to Westminster on Tuesday.

Sarah Pochin, Reform UK's first female MP, was grinning from ear to ear when she appeared for a photocall outside parliament, flanked by Nigel Farage and Lee Anderson, just before being sworn in.

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The six votes that took her over the line at the Runcorn and Helsby by-election was the omen of things to come on Friday morning. It's no exaggeration to say British politics may never be the same again.

Up and down the country, Farage's party is now settling into power at a local level. Before the local election results, the Reform leader told Beth Rigby the party's biggest risk was succeeding and not delivering.

I asked Dame Andrea Jenkyns, as she was sworn in as Reform's new mayor for Greater Lincolnshire, if she is ready for the responsibility, and she told me: "I'm going to exceed expectations."

She talks a lot about saving money - has she worked out how much?

"It's my first day in the job, I'll know in a few weeks once I've seen the figures," she said.

How will Labour respond?

Reform UK may be grappling with exactly how to deliver in local government but, for now, the afterglow of last week's success is sustaining them. They showed they are a real threat to not just the Conservatives but to Labour too, and it's not clear there is a consensus in the Labour Party on how to respond.

"Labour needs to listen!" and "get behind the working class again!" were among the messages from Labour MPs writing in the newspapers over the weekend.

The trade unions are wading in too - the leader of the General Federation of Trade Unions tells me the results represent "deep-seated anger" that proves the need for an "end to austerity".

There is plenty of advice. The question the government really needs to ask itself now is whether to fight Reform UK on their turf - and there are already signs of that with immigration briefings earlier on Tuesday - or whether to try to tell their own story.

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The Conservatives have learnt the hard way the challenge of the former as the embattled Tory leader Kemi Badenoch trudges on, saying she is changing the party "to be one that is tougher on immigration".

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The decision about whether to tell another story all together, rather than take the fight to Reform's preferred territory, is one that Labour needs to work out.

It's a choice that could define this government.