The unofficial title 'Father of the House' is given to the MP with the longest unbroken service in the House of Commons.
The main responsibility of the Father is to preside over the election of a Speaker at the beginning of a new Parliament or if the previous Speaker has ceased to be an MP.
Sir Edward Heath, former Conservative Prime Minister held the position from 1992, followed by Labour veteran Tam Dalyell in 2001.
Historically, it has nearly always been backbench MPs who qualify for this title, but occasionally a serving minister may become Father of the House.
For example, Sir Henry Campbell-Bannerman was PM and Father simultaneously in 1907-8.
Any Father of the House who also occupied a ministerial post would be forbidden from presiding over a Speaker's election - and a replacement would need to be found.
Seniority of Members
When two MPs have served for an identical period, the one who took the Oath first becomes Father.
Thus, Sir Bernard Braine - later Lord Braine - assumed the title in 1987 rather than (Sir) Edward Heath, although both had been elected in 1950.
Michael Foot, who was in the same Parliament, first became an MP in 1945, but his service had not been continuous and was therefore not eligible to become Father.