Anthony Neil Wedgwood Benn (3 April 1925 - 14 March 2014), originally known as Anthony Wedgwood Benn, but later as Tony Benn, was a British politician, writer, and diarist. He was a Member of Parliament (MP) for 47 years between the 1950 and 2001 general elections and a Cabinet minister in the Labour governments of Harold Wilson and James Callaghan in the 1960s and 1970s. Originally a moderate, he was identified as being on the party's hard left from the early 1980s, and was widely seen as a key proponent of democratic socialism within the party. Benn inherited a peerage on his father's death (as 2nd Viscount Stansgate), which prevented his continuing as an MP.
Peerage reform
Benn's father had been created Viscount Stansgate in 1942 when Winston Churchill increased the number of Labour peers to aid political work in the House of Lords; at this time, Benn's elder brother Michael was intending to enter the priesthood and had no objections to inheriting a peerage. However, Michael was later killed in an accident while on active service in the Second World War, and this left Benn as the heir to the peerage. He made several unsuccessful attempts to renounce the succession.  In November 1960, Lord Stansgate died. Benn automatically became a peer, preventing him from sitting in the House of Commons. The Speaker of the Commons, Sir Harry Hylton-Foster, did not allow him to deliver a speech from the bar of the House of Commons in April 1961 when the by-election was being called. Continuing to maintain his right to abandon his peerage, Benn fought to retain his seat in a by-election caused by his succession on 4 May 1961. Although he was disqualified from taking his seat, he was re-elected. An election court found that the voters were fully aware that Benn was disqualified, and declared the seat won by the Conservative runner-up, Malcolm St Clair, who was at the time also the heir presumptive to a peerage.  Benn continued his campaign outside Parliament. Within two years, though, the Conservative Government of the time, which had members in the same or similar situation to Benn's (i.e., who were going to receive title, or who had already applied for writs of summons), changed the law. The Peerage Act 1963, allowing lifetime disclaimer of peerages, became law shortly after 6 pm on 31 July 1963. Benn was the first peer to renounce his title, doing so at 6.22 pm that day. St Clair, fulfilling a promise he had made at the time of his election, then accepted the office of Steward of the Manor of Northstead, disqualifying himself from the House (outright resignation not being possible). Benn returned to the Commons after winning a by-election on 20 August 1963.

Q: What is peerage?
A: Labour peers to aid political work in the House of Lords;

Q: How was it reformed?
A: The Peerage Act 1963, allowing lifetime disclaimer of peerages,

Q: What was disclaimer of peerages?
A: Benn was the first peer to renounce his title,

Q: Why did he renounce his title?
A: Benn automatically became a peer, preventing him from sitting in the House of Commons.
Why did he automatically become peer?
In November 1960, Lord Stansgate died.
In November 1960, Lord Stansgate died.