By 2015 he was the longest-serving member of his party's House of Commons delegation, and was the last Liberal Democrat MP to have experience of Parliament in the 1970s.

Beith was elevated as a life peer in the 2015 Dissolution Honours List[3] and took his title and a seat on the House of Lords Opposition benches on 23 November 2015.

He was educated at The King's School, Macclesfield before going to Balliol College, Oxford, where he read Philosophy, Politics and Economics graduating in 1964.

He contested Berwick-upon-Tweed as the Liberal candidate at the 1970 general election but was heavily defeated by the sitting Conservative MP Antony Lambton.

Just three months after his by-election success, Beith was out canvassing his constituents again at the February 1974 general election, being returned to Parliament with an increased majority of 443.

Beith stayed on as Deputy Leader of the Liberal Democrats following the 1992 general election under Ashdown until 2003, and was sworn of the Privy Council in 1992.

Following Sir Menzies Campbell's resignation as Leader of the Liberal Democrats on 15 October 2007, Beith was encouraged to stand as a prospective compromise candidate for the Lib Dem leadership.

On 19 May 2009, Beith was the first MP to declare his candidacy to succeed Speaker Michael Martin, who stood down from the position on 21 June 2009.

[18] He was announced as a life peer in the 2015 Dissolution Honours and was created Baron Beith, of Berwick-upon-Tweed in the County of Northumberland on the afternoon of 19 October.

[29] Until her death on 26 June 2020, Lord Beith and Baroness Maddock divided their time between homes at Berwick-upon-Tweed, Northumberland, and London SW1; they were one of the few married couples both titled in their own right.

[30] Lord Beith serves as President of the Liberal Democrat Christian Forum and of the Historic Chapels Trust, a charity he helped to found and of which he was Chair of Trustees between 2001 and 2014.