Keir Mather - Labour's newest MP and 'baby of the House'

Labour's Keir Mather has become the youngest MP in the House of Commons.

He won the Selby and Ainsty by-election after overturning a 20,137 majority and has been nicknamed the "baby of the House".

But who is Labour's new MP for the North Yorkshire constituency?

Born in 1998, Mr Mather has become Westminster's youngest MP, at 25 years old.

According to his party biography, Mr Mather was born in Hull and grew up near Selby.

As a child, Mr Mather joined the youth parliament and set up a Labour group for young people in Hull, his mother has said.

"He just loves speaking," said mum Jill Tambaros, adding that he had studied Speech and Drama in school and enjoyed performing in plays.

"We both just really enjoy politics, it's just part of our life," she told BBC News. "If ever I was cross with him he'd go, 'mummy, shall I put on BBC News?' - to cheer me up."

He was named after James Keir Hardie, one of the founders of the Labour party, Ms Tambaros added.

After school, the young Keir went on to study history and politics at Oxford University, graduating with a first-class degree - according to his LinkedIn profile.

Mr Mather has previously worked as a parliamentary researcher for shadow health secretary Wes Streeting, and more recently as a senior public affairs adviser at the Confederation of British Industry (CBI).

He also became a political leadership scholar at the Blavatnik School of Government, according to the University of Oxford.

In a video on Labour's website, Mr Mather says he grew up in Brough, a village in the East Riding area of Yorkshire, and supports the rugby league team Hull Kingston Rovers.

"There isn't much I love more than being down on the terraces, a place where people come together, where you're part of a community and you sing with one voice."

After winning his seat in the North Yorkshire constituency, with a majority of 4,161, Mr Mather said he "understood the enormity of what has just happened".

When asked how he felt about becoming the "baby of the House", he joked that he had "heard far worse".

Mr Mather's mother described her son as articulate, observant and genuine, predicting he will do "very well" in the House of Commons.

"Nothing really phases him, he doesn't get stressed...he just takes things in his stride, one step at a time," said Ms Tambaros.

Asked is he could be a future prime minister, she replied: "Why not? Never say never...he's 25 and he's done all of this!"

Labour leader Keir Starmer said the new MP would be a "fantastic MP who'll deliver the fresh start that Selby and Ainsty deserves".

Labour's deputy leader, Angela Rayner, described the result in Selby and Ainsty as a "historic win", adding she was "pretty certain [Mr Mather]... understands some of the challenges his generation faces".

Speaking on BBC Breakfast, Ms Rayner said: "Being 25, he's of that generation that is looking at insecure work, looking at not being able to ever own their own home - and looking at the challenges that they face with cost of living now, that leaves them in this spiral of not being able to get on in life."