The idea of a long-serving prime minister - undefeated at the polls - being ousted by an internal party ballot might at first sight seem bizarre.

Both men were long-serving ministers of Justinian I (r. 527-565) and Justin would want to replace them with his own loyalists.

He kept his position despite a wave of dismissals of other long-serving ministers and key officials.

Guelleh retained Dileita in his post even though various other long-serving ministers were dropped from the new government that was announced on 12 May.

A business manager and long-serving minister, Nika Gilauri became prime minister in February 2009.

Brian Mulroney, a long-serving Conservative prime minister, was Power's outside labor lawyer well before he entered politics.

Salter's father, William Salter, was a long-serving Congregational minister in Burlington, Iowa.

Yet Havel made no secret of his dislike of Vaclav Klaus, the long-serving first non-communist prime minister.

Vartkes Kassouni, a long-serving minister of the Armenian Evangelical Church (1957-present) who lives in California, United States.

Two long-serving ministers, Dr Brian Mawhinney, who has been there since 1986, and Mr Richard Needham, since 1985, both return to senior posts in mainland ministries.