An extraordinary result followed an extraordinary few weeks.

Here's what's happened:

• Labour have held on to the seat of Batley and Spen with just over 13,000 votes after a fraught and divisive campaign
• The Conservatives came in second place, narrowly losing their opportunity to take the seat
• Labour's majority is now 323 votes, it was 3,525 last time the constituency voted in the 2019 general election
• Sir Keir said he was "so delighted" when the news of the by-election came through
• He said the people of Batley and Spen had elected a "champion" in their community
• He hailed the victory as a "victory for the Labour movement" and said "Labour is back"
• The result has arrested speculation of a mounting leadership bid against Sir Keir Starmer from those on the party's Left

That's where we'll leave our live page coverage of the by-election.

You can continue to follow the story on the BBC News website, as well as analysis from our political correspondent Iain Watson on How Labour held on - and what it means for Sir Keir Starmer.

Thanks for joining us.

Image source, Getty Images

The Mayor of London has denied the narrow result at Batley and Spen still left questions over Sir Keir Starmer's leadership of the Labour Party.

Sadiq Khan says it's "great" that Kim Leadbeater managed to see off her Conservative rival Ryan Stephenson with a narrow margin of 323 votes, saying "a win's a win".

"Keir's the most humble person in Parliament, he understands the challenges he's got as the leader," he says.

"He recognises that our defeat in 2019 was a historic low, and there's a huge amount of building required."

Khan also says the "awful" campaign in the West Yorkshire constituency had been "divisive and full of hatred".

Here's the moment Sir Keir Starmer declares Kim Leadbeater's win as a "fantastic victory".

He says she epitomises everything he wants the Labour Party to be.

Labour win has bought Starmer some breathing spacepublished at 12:31 British Summer Time 2 July 2021

12:31 BST 2 July 2021

Lewis Goodall
Political correspondent

The Batley and Spen constituency has been Labour since 1997, and it is the 11th year of a Conservative government of one form or another.

The Tories really ought to not be in contention at all, and there was still a swing from Labour to Conservative – a 2.9% swing.

Now if that happened at a general election, Labour would lose seats elsewhere, they would go backwards. But you have to treat it with a bit of caution because George Galloway's presence does distort things a bit, it’s a bit difficult to extrapolate.

Keir Starmer will be a very relieved man. After the Hartlepool by-election, he really couldn’t afford another loss.

This has bought him some time, breathing space into the summer and into the party conference to rethink and reconsider his strategy.

As for Prime Minister Boris Johnson, though he remains dominant, this, alongside the Chesham and Amersham by-election (where the Lib Dems overturned a large Conservative majority) have told us that there are limits to that dominance.

Something that we couldn’t be sure of only a few weeks ago.

Sir Keir is asked whether this is a victory for Kim Leadbeater personally, rather than the Labour Party.

"Of course it is a victory for Kim... but this is a victory for the Labour movement," Sir Keir replies.

"Those core Labour values can win out, and they will win out.

"The divisive politics probably took 8,000 votes from Labour, so there was an attempt to divide the Labour vote and Kim won," he says, adding the Tories thought they could "sit back" and expect to win.

Former Tory voters voted Labour, he states.

"When the Labour Party sticks to its core values... we can win just as we won here, this is just the start, Labour is back," he finishes.

Labour leader Sir Keir Starmer says he "didn't sleep" last night, but was "so delighted when this news [Labour holding the seat in the by-election] came through".

He says in Kim Leadbeater, the people of Batley and Spen have "a champion in their community".

He's asked if Boris Johnson not sacking former health secretary Matt Hancock hurt the Conservatives during the by-election.

"People are getting fed up with the politics of misinformation, half truths, untruths," he says. "It's about decency and integrity," he says, adding this is the "wider battle of modern politics".

He's asked if the prime minister has "peaked".

Sir Keir says there is a "gulf" between integrity, honesty and bringing people together and mistruths and half truths.

Why did Labour win?published at 12:13 British Summer Time 2 July 2021

12:13 BST 2 July 2021

Lewis Goodall
Political correspondent

The fact that Labour won and got so many votes suggests that Labour’s victory is actually a little bit more impressive than the headline majority might suggest.

Without George Galloway standing it would probably have been a bigger victory.

The fact Labour won despite leaking so many votes to Galloway suggests they may have done a bit better with their party’s traditional vote and maybe even with potential Tory switchers. Certainly they may have done better with Lib Dem voters who appear to have voted tactically for Labour.

Labour’s get-out-the-vote operation was also very successful. And what’s behind it?

Well, Kim Leadbeater herself, very much a local candidate and respected locally.

The Conservative lead is still pretty gaping nationally in the polls, but it has narrowed a touch in recent weeks.

Perhaps the result of the Matt Hancock affair, perhaps the vaccine shine becoming a little less lustrous.

If Labour had a "less talented" candidate than Kim Leadbeater in Batley and Spen maybe they would have lost the seat, Ash Sarkar, contributing editor at Novara Media told BBC News.

"In a really challenging campaign, where she did have it tougher than most, there were personal attacks there was harrassment there was all sorts of nasty behaviour, she not only stood her ground but managed to hold onto the seat in there really challenging circumstances."

She says: "I don't think [Labour] controlled the narrative, I think they were trying to get their excuses in early and then an astonishingly talented candidate, Kim Leadbeater and a really good get out the vote operation, provided a surprise victory for the party."

She says she thinks there are still big challenges for Labour and for Sir Keir Starmer but he can look at this result as "a bit of a reprieve".

How Labour held on - and what it means for Starmerpublished at 11:54 British Summer Time 2 July 2021

11:54 BST 2 July 2021

Image source, Getty Images

Holding Batley and Spen will feel like a by-election gain for Labour - so how did they do it?

BBC political correspondent Iain Watson looks at the campaign in Batley and Spen and what the consequences are for the Labour party and leader Sir Keir Starmer.

"This campaign has been tough, because others have poisoned it... with lies, harassment, threats and intimidation," Sir Keir Starmer states.

"That that should have happened to Kim, of all people, is unforgivable," he says, for those who didn't call it out "they should be utterly ashamed of themselves".

"Labour is back," he states.

"Labour is coming home," he finishes, to rounds of applause from the assembled activists.

Labour leader Sir Keir Starmer addresses activists gathered in the constituency, praising the Labour win, saying "what a fantastic victory... of hope over division".

He thanks them for the "blood you have sweated" to knock on doors up and down the constituency.

He says it took "incredible courage" for Leadbeater to stand for the seat: "Everybody knows Kim," because she is a local candidate, he states.

"She believes in truth and honesty, in bringing people together, and that's exactly what I want in our Labour Party."

He says that Jo Cox would "so proud to see you today" heading to Parliament.

"We want you down in Parliament," he says he will be "so proud" when she is sworn in as the new MP on Monday.

Kim Leadbeater says her first priority as MP of Batley and Spen is to get people together for conversations that will make a difference.

She told BBC News: "The message now is let's think about the way that we want our country to be run, the way that we want our politics to be done. Let's think about what it means to people."

She says she is concerned about the number of people who don't vote "because they're just disengaged with it".

"I don't blame them for not coming out and voting when they've seen some of the scenes they've seen over the last few weeks. So let's think about how we can make politics more relateable and how we can engage people with it more," she says.

"My first priority is to start getting people together, that's my big thing, that's one of the things I'm good at.

"So whether it's crime and antisocial behaviour, whether it's the state of the roads, who are the people who can make a difference, who are the people who can act on these things, let's get the councillors together, let's get the police involved let's look at where we can get some funding, get people around the table and have those conversations."

Labour's narrow slither of a victorypublished at 11:30 British Summer Time 2 July 2021

11:30 BST 2 July 2021

Lewis Goodall
Political correspondent

Labour has pulled off what a few days ago many pundits said was a lost cause entirely.

In fact, they have held on to Batley and Spen in West Yorkshire. It was a narrow slither of a victory, with a 323 vote majority.

Two factors made people think Labour was finished here today.

One was George Galloway standing, targeting the British Muslim vote in the constituency which is sizable, so people assumed that would eat into the Labour vote.

And then if we go back to the 2019 election there was another independent candidate at that time running for the seat.

They did very well at the other end of the spectrum, they were pro-Brexit. Without him standing this time around it was assumed that his votes would bolster the Conservative vote.

Put the two together, with the fact that the Conservatives are polling very well nationally at the moment, and people assumed that a Tory victory would be at hand. And it didn’t happen.

In case you're just joining us, here's a round-up of what's happening:

• Labour have held on to the seat of Batley and Spen with just over 13,000 votes after a fraught and divisive campaign
• The Conservatives came in second place, narrowly losing their opportunity to take the seat
• Labour's majority is now 323 votes, it was 3,525 last time the constituency voted in the 2019 general election
• George Galloway's Workers Party polled at 8,264 votes, and he has said he will form a legal case to challenge the result
• The result has slowed speculation of a leadership challenge to Sir Keir Starmer
• The Conservatives have attributed the loss to recent revelations around Matt Hancock's personal life, as well as "other factors"

Kim Leadbeater's win had additional political significance, an Oxford University professor says.

Jane Green, professor of political science at Nuffield College, told BBC News: "Kim Leadbeater was a very popular local campaigner, the only local candidate and of course hugely emotive, hugely significant and symbolic there in Batley and Spen.

"So it's a great result for Labour, I do think it's a remarkable result given the challenges that they were up against in Batley and Spen.

"But I think they also have to really look at this result and see what was it that managed to get people to vote for Kim Leadbeater and can they replicate that in future and we just have to wait to see if they can do that."

She says votes for candidate George Galloway "quite possibly" could have gone to Labour but had he not been running Labour could have gained votes from Brexit party supporters.

"And also had he not run there might not have been a backlash against that by perhaps more moderate Conservative, maybe Consertaive remainers, maybe Liberal Democrat voters who in this instance voted for the Labour Party," she says.

Labour still has questions to answer around why many people looked to Galloway as an alternative, she says.

But the party "deserves credit for this win against expectations which means it has additional political significance", she says.

Image source, Getty Images

Kim Leadbeater says a key part of her by-election success was being "born and bred" in the area.

So who is the new Labour MP? Read more here.

The by-election in Batley and Spen is the fourth UK Parliament by-election to be held this year.

In May, the Conservatives beat Labour in the Hartlepool by-election. when Tory candidate Jill Mortimer defeated Labour rival Paul Williams by nearly 7,000 votes.

There was a 16% swing from Labour to the Conservatives and it was the first time since the constituency was formed in 1974 that it had turned blue.

The result was a blow to Sir Keir Starmer's efforts to win back support in traditional Labour heartlands and came as the Tories also made gains from Labour in English council elections.

Later that same month, a by-election was held in Airdrie and Shotts and was won by the SNP after the party saw off a challenge from Labour.

Anum Qaisar-Javed won the seat for the SNP with a reduced majority of 1,757 over her Labour opponent.

In June there was a blow to the Conservatives, when the Liberal Democrats pulled off a stunning by-election victory in Chesham and Amersham and overturned a 16,000 majority in a seat that has always voted Conservative.

The Lib Dems' candidate Sarah Green won by 8,028 votes from the Tories, with the Green Party in third place.

Labour had the worst by-election result in the party's history, with 622 votes.

The co-chair of Momentum, the group which helped Jeremy Corbyn to victory in his 2015 candidate for Labour leadership, Andrew Scattergood, says "this is a great result for Kim Leadbeater".

"I think she ran a great campaign," he states, "but let's not kid ourselves here."

Labour have just "squeaked" a victory in a seat which was already Labour, he says.

"We need to be thinking about what we should do next," and he criticises the lack of policies that have been put out by the Labour Party.

"Whoever the leader of the Labour Party is, needs to be thinking about what's going wrong," he says. "We are heading towards not being able to win in any general election that's coming up."

He says this needs to be a "massive wake-up call" for Sir Keir Starmer.