Keir Mather was first elected as the Labour MP for Selby & Ainsty in a July 2023 by-election caused by the resignation of the former Conservative MP, Nigel Adams. He gained the seat for Labour with a majority of 4,161.
The constituency of Selby and Ainsty is found in the southern part of North Yorkshire, and contains the towns of Selby and Tadcaster, in a rural belt between Leeds and York.  The John Smiths beer factory is found in this constituency at Tadcaster.  It had been won by the Conservatives in the 2019 general election with a majority of 20,137.
In July 2023, Mr Mather became the youngest MP in the House of Commons, earning him the title, ‘the baby of the house’. He was born in Hull in 1998.
Mr Mather read history and politics at Oxford University, graduating with a first-class degree. He became a political leadership scholar at the Blavatnik School of Government.
