the by-election was triggered when tony blair, the labour party member of parliament (mp) for sedgefield and former prime minister, "resigned" to become envoy for the international diplomatic quartet on the middle east. to resign as an mp, blair accepted the office of steward and bailiff of the three hundreds of chiltern, thereby deliberately disqualifying himself from parliament and causing the by-election. blair had held the constituency since its creation for the 1983 election, and labour had held its predecessor constituencies since the 1935 election.