The Father of the House is an honourary title given to the longest continuously serving member of the UK's House of Commons - one of the houses of parliament. That is, the member who has had the longest unbroken service in the house.
The Father of the House at the time of writing (December 2002) is Tam Dalyell, who has served constantly since he was elected to the house in June 1962. When he steps down, it looks like his successor may be the first Mother of the House - Gwyneth Dunwoody.
In the event that two members entered the house on the same election, and both would be Father, the one who first took the Oath is given the role.
Although the title is not explicitly defined in the House of Commons Standing Orders, the Father of the House (provided he has not been a Minister) is responsible for standing-in should the Speaker leave the house for any reason - he should oversee the election of the new Speaker. This is his sole official duty - although he has numerous unofficial duties.
The Father of the House is typically, but not necessarily, a member of the Select Committee on Privileges. He is also called upon to speak on ceremonial occasions in the house, and to add input to debates where historical precedents or perspective might be relevant.
The selection process has not always been as clear-cut as the current system. Historically, there is evidence of many selection systems including:
- Election by members
- Longest aggregate service (rather than unbroken)
- Time since first entering the house
But, since the system is purely a tradition, and not a written rule, it can change at any time.
Interestingly, in the 1950s, although Winston Churchill had entered the house in 1900 and was the oldest member, his break of only a few months in 1923 resulted in his disqualification until 1959 when David Grenfell left the house, having served since 1922.
Thanks to CatherineB for info on Gwyneth Dunwoody.