He has twice held the leading political role in London local government : firstly as leader of the Greater London Council from 1981 until the council was abolished in 1986 by the government of Margaret Thatcher , and secondly as the first Mayor of London , a post he held from its creation in 2000 until 2008 . During his political career , he has twice held the leading political role in London local government , firstly as Leader of the Greater London Council from 1981 until the council was abolished in 1986 , and secondly as the first elected Mayor of London , a post he held from its creation in 2000 until 2008 .