There'll be more reaction and analysis on BBC Cymru Wales services from 6am.

In the meantime, here's a summary of what happened.

Felicity Evans
BBC Wales political editor

This is a good hold for Labour and Ruth Jones will be pleased to be heading for Westminster with a majority of nearly two thousand at a time of such unpredictability.

The Conservatives will be pleased to have held off the UKIP challenge for second place when the UK government is under such pressure over Brexit.

But UKIP is taking encouragement from a vote share of more than 8 per cent, which would be their base line for keeping a presence in the Senedd at the next Welsh Assembly elections.

What happened in this by-election should not be taken as a barometer for for future elections - politics is a rollercoaster right now.

Ruth Jones will need to fasten her seat belt.

Conservative vice-chairman Alec Shelbrooke disputes a suggestion his party should be scared of UKIP:

Labour leader Jeremy Corbyn said:

“Ruth will be a fantastic successor to Paul Flynn and will take up the tireless work he carried out for this community," he said.

“Tonight’s result sends a clear message that the people of Newport and Wales are fed up of austerity which has robbed the Welsh economy of £1bn through needless cuts, and shows support for Labour’s alternative."

Conservative candidate Matthew Evans, who came second, said he noticed a lot of anger from voters over Brexit confusion.

“Whether they voted Leave or Remain people want clarity and they deserve that clarity," he told BBC Wales.

“Hopefully this issue will be resolved shortly.”

Ruth Jones said she was “incredibly grateful” to the voters of Newport West.

“There is a level of distrust of all politicians at the moment,” she told BBC Wales, “because of what’s been going on in the House of Commons.

“I think that highlighted itself in the relatively low turnout.

“I want to reach out to those who didn’t go out to vote today to make sure that we get their voices heard and we get re-engaged with politics again.

Asked her lower majority, she said: “Paul had a massive personal vote. I’m not surprised. I’m grateful we’ve got the majority we have.”

On how she would vote on Brexit, she said: “It’s difficult to say exactly what I would or wouldn’t do. I don’t know what’s on the table at the moment.”

Cardiff University Professor Roger Awan-Scully on the state of the parties:

Initial thoughts from Cardiff University political expert

Ruth Jones has won the Newport West by-election for Labour with a majority of 1,951 over the Conservatives.

Neil Hamilton came third for UKIP, followed by Plaid Cymru and the Liberal Democrats.

Ruth Jones (Labour) - 9,308

Matthew Evans (Conservative) - 7,357

Neil Hamilton (UKIP) - 2,023

Jonathan Clark (Plaid Cymru) - 1,185

Ryan Jones (Liberal Democrats) - 1,088

Amelia Womack (Green Party) - 924

June Davies (Renew) - 879

Richard Suchorzewski (Abolish the Welsh Assembly Party) - 205

Ian McLean (SDP) - 202

Philip Taylor (Democrats and Veterans) - 185

Hugh Nicklin (For Britain) - 159

Andrew Neil of BBC One's This Week quizzes UKIP candidate Neil Hamilton on his party's performance and recent direction.

Former Lib Dem AM Bill Powell said the party had been “squeezed” in the by-election campaign but he said some voters liked what the party were saying on the need for a further referendum on Brexit.

Plaid Cymru AM Delyth Jewell said Newport West wasn’t an area where the party had traditionally been strong but she felt that Plaid would have an improved performance.

Alec Shelbrooke, vice-chair of the Conservative Party and MP for Elmet and Rothwell told BBC One's This Week it would be a “seismic shock” if they were to win the seat.

He said the Tories had put a “respectable” amount of effort into a campaign they fought on local issues such as the M4 relief road.

He also suggested that Labour had “put a huge amount of resource” into fighting to keep a seat which had been Labour for most of its existence.

Labour’s Shadow Defence Secretary Nia Griffith told Andrew Neil on BBC One’s This Week that the issues she heard on the doorstep in Newport West were “a mixture of everything”.

These include concerns about crime rates, police cuts and “nine years of austerity”.

The Llanelli MP added: “It’s a difficult time with a general feeling that people are fed up with politics.”

Cardiff University's Prof Roger Awan-Scully says that a 37.1% turnout is low.

"Far from a historic low - but still unquestionably poor," he says.

"The next big question - will this low turnout hurt any party in particular?"

One of Newport West's predecessor constituencies, Monmouth Boroughs, was won four times by Victorian ironmaster Crawshay Bailey, external.

Also known as Cosher Bailey, he was the inspiration behind a well-known song - “Did you ever see such a funny thing before?”

The turnout was 37.1%

At the 2017 general election it was 67.5%