Paul Pigott
BBC News

"You'll forgive me, I’m not used to speaking first in these election counts.

"Whilst we are perhaps euphoric in some parties tonight, I would respectfully ask you to remember please why we are having this election under very sad circumstances and I am very proud.

"This is hard... to pay tribute to Hefin David and to his family and friends I extend my still, personal deepest sympathies. He will be a hard act to follow.

"I will never fill his shoes, but I promise you I will walk the same path that he did and I can pay no finer tribute to an excellent man.

"I hope that this will be now an exciting time for politics in Wales.

"I’ve been absolutely heartened by the number of young people who’ve been involved in this campaign.

"A lot of them are standing to my right.

"Across the entire constituency, people not interested in politics... I've had selfies taken, I've never had this.

"Listen now, Cardiff and listen Westminster, this is Caerphilly and Wales telling you we want a better deal for every corner of Wales.

"The big parties need to sit up and take notice.

"Wales, we are at the dawn of new leadership, at the dawn of a new beginning, and I look forward to playing my part for a new Wales and in particular for the people of the Caerphilly constituency - I thank you with all of my heart.

"This is better than scoring the winning try for Wales against New Zealand in the Rugby World Cup.

"This means everything to me and, the people of Caerphilly constituency, you mean everything to me and I promise you I will serve you to the very best of my ability.

"Diolch yn fawr i chi."

Image source, PA Media

Analysispublished at 04:25 BST

04:25 BST

Gareth Lewis
BBC Wales political editor

A result of 11% looks dreadful for Labour. If that were extrapolated across Wales at next May's Senedd election then the party would be on the verge of a wipe out. What the party does between now and then could be crucial to their very survival, let alone survival as a political force.

There is still a long time to go until May, but the end of their dominance here in Caerphilly has come in decisive fashion.

Image source, PA Media

Mark Palmer
Assistant editor, BBC Wales

Image source, Mark Lewis/BBC

Echoing the words of the former Labour MP for Caerphilly Ron Davies when Wales said "yes" to devolution in 1997, Plaid Cymru’s Westminster leader Liz Saville-Roberts says: "It is a very good morning in Wales."

Writing on X, Saville-Roberts pays tribute to the "legendary Lindsay Whittle".

"Congratulations on your historic victory for Plaid Cymru.

"My heart’s thanks to the people of Caerphilly".

Labour dominance in Wales well and truly under threatpublished at 03:43 BST

03:43 BST

Gareth Lewis
BBC Wales political editor

Remember the date: in the early hours of 24 October more than a century of Labour dominance in Caerphilly came to a shattering end.

Plaid Cymru is jubilant with its winning candidate, Lindsay Whittle, describing their opponents as a "fatally wounded animal".

The party will now set its sights on repeating the result at next year's Senedd election.

Plaid feels it's persuading voters that it is a viable alternative to Labour ahead of a crucial year in Welsh politics.

There are lessons for Reform - who would have expected a closer race - as despite a high turnout, it did not persuade enough voters to back Llyr Powell.

For Labour, there is precious little time to regroup, with the party's MS's meeting in the Senedd on Friday morning.

If there was any doubt before today, more than a century of Labour dominance across the whole of Wales is now under serious threat.

Image source, PA Media

Zia Yusuf, Reform UK’s head of policy, has congratulated Plaid Cymru on victory, describing his own party’s performance as "remarkable".

"This is a historic realignment in Welsh and British politics. The Senedd elections next May are now a battle between Reform and Plaid," he said in a post on X, saying Labour’s vote in the constituency had collapsed.

David Deans
BBC Wales political reporter

Eluned Morgan has congratulated Lindsay Whittle in a statement, adding that the by-election was held in the "toughest of circumstances, and in the midst of difficult headwinds nationally".

"Welsh Labour has heard the frustration on doorsteps in Caerphilly that the need to feel change in people’s lives has not been quick enough.

"We take our share of the responsibility for this result. We are listening, we are learning the lessons, and we will be come back stronger."

David Deans
BBC Wales political reporter

The council workers are starting to clear up now - with boxes of stuff being wheeled out.

Lindsay Whittle still has a row of people waiting to interview him, with a group of Plaid Cymru staff and activists hanging around to enjoy their victory.

This by-election has had more press attention than perhaps some full blown Welsh Parliament elections - driven by Labour's difficulties at the hands of Reform.

Journalists are here now writing their final stories, with some reflecting perhaps that it might be harder for Reform to win seats in Wales than some had thought.

But it's difficult to exaggerate how a big deal this by-election is - ending up being a two-horse race between a party which barely existed a few years ago, and another which has never won Caerphilly before, with Labour a distant third in its heartland.

Oscar Edwards
BBC Wales

David Deans
BBC Wales political reporter

For Labour, tonight's result means governing gets harder - literally by one Senedd member.

Eluned Morgan's Welsh government now needs to find someone else to get its spending plans for the Welsh NHS, education and everything else it does. Last year it just needed the Welsh Lib Dem Jane Dodds.

Before the death of Hefin David, Labour had exactly half the seats in the Welsh Parliament and was a seat short of a majority. Now it is two seats short.

It's also a huge psychological blow - Caerphilly having been dominated by Labour in one way or another all the way back to the 1920s.

For Plaid Cymru, this is a big deal. In a high profile by-election, the party has beaten Labour significantly.

It's a big boost for the party months ahead of a crucial Senedd election, where its hoping it can form the next Welsh government.

Oliver Slow
BBC Wales

Image source, Matthew Horwood

Labour candidate Richard Tunnicliffe, who came a distant third in the vote, thanked those who voted for his party, congratulating Plaid Cymru on their victory.

He also said it was a by-election "nobody expected" to take place, paying tribute to former Member of the Senedd (MS) Hefin David.

"Hefin was my friend and my mentor," he said.

"His kindness, his passion for the people of Caerphilly and his tirelessness in standing up for his constituents has been the guiding spirit of our campaign."

He also said his party would focus on preparing for next year’s Senedd election, hoping to send a message that they can "make a difference" in people’s lives.

Oscar Edwards
BBC Wales

Strong words from the Reform candidate following the result.

He's angry about Labour's campaign, saying: "I'm very disappointed and thankfully the voters had seen through their smear, fear.

He adds: "They deserved to be in the gutter like their campaign belonged."

Powell has left the building as the Plaid celebrations continue.

David Deans
BBC Wales political reporter

Powell came second tonight. He didn't give a speech at the podium but he did speak to a scrum of media, where he said he was proud of the campaign his party had run.

"Our ground campaign is going to get better," he said.

Referencing next year's Welsh Parliament election, he said: "I think next May we're going to form a Reform government.

"We've got more people turning out to vote now when they've got a party they believe in."

Oliver Slow
BBC Wales

Image source, PA Media

Plaid Cymru leader Rhun ap Iorwerth said the people of Caerphilly have "spoken loud and clear", saying they had backed his party’s “positive, pro-Wales vision”.

"This result shows that Plaid is no longer just an alternative," he said in a statement.

He described Lindsay Whittle as a "tireless local champion".

"[He] knows every community in this constituency inside out and will deliver real change for the people of Caerphilly," ap Iorwerth said.

Mark Palmer
Assistant editor, BBC Wales

Image source, Mark Lewis/BBC

It's 14th time lucky for Lindsay Whittle.

The Plaid candidate has stood time and time again in the constituency at elections for Westminster and Cardiff Bay since 1983.

He now has the chance to shape the town that he was born in.

Mark Palmer
Assistant editor, BBC Wales

Lindsay Whittle pays tribute to Hefin David saying he will be a "hard act to follow".

"I will never fill his shoes but I assure you I will walk the same path that he did."

He urges Cardiff and Westminster to listen saying he wants a "better deal" for every corner of Wales.

"The big parties need to sit up and take notice.

"We are at the dawn of a new beginning”.

Huge cheers as Plaid victory announcedpublished at 02:19 BST

02:19 BST

Gareth Lewis
BBC Wales political editor

There are huge cheers in the hall and chants of "Wales, Wales" as Lindsay Whittle’s victory is announced.

He cracks a joke to start his acceptance speech saying he’s not used to speaking first.

This is a win in the Caerphilly constituency for Whittle at the 14th time of asking.

He nearly breaks down in tears paying tribute to the constituency's late MS Hefin David as he warns Westminster and Cardiff Bay that Wales needs a better deal.

"This is the start of a new dawn," he adds.

Here’s the final number of votes for each candidate:

• Steve Aicheler - Welsh Liberal Democrats - 497
• Anthony Cook – Gwlad - 117
• Gareth Hughes - Green Party - 516
• Gareth Potter - Welsh Conservatives - 690
• Llyr Powell - Reform UK – 12,113
• Roger Quilliam – UKIP - 79
• Richard Tunnicliffe - Welsh Labour – 3,713
• Lindsay Whittle - Plaid Cymru – 15,961

Lindsay Whittle is Caerphilly's new Member of the Senedd.

Candidates are on the stage.

We're about to hear the result.