The GLA is a democratically-elected strategic authority, comprising two distinct parts: the Mayor and Assembly. The Mayor is elected directly by Londoners, while the Assembly consists of 25 elected members (14 representing constituencies and the rest elected from party lists according to total London-wide vote).
There is a clear separation of powers between the Mayor and the Assembly. The Mayor has an executive role, setting an overall vision for London and defining clear strategies on a range of issues (including air quality, spatial development, culture and tourism, economic development, transport and waste), while the Assembly members act as scrutineers, with the power to veto the Mayor’s budget plans (but only with a two-thirds majority).
This system of 'checks and balances' has generally worked very well since the GLA started in 2000.
Much of the work of the GLA is carried out by four executive or functional bodies, Transport for London (TfL), the London Development Agency (LDA), the Mayor's Office for Policing and Crime (MOPC) and the London Fire and Emergency Planning Authority (LFEPA). Details of the role of each of these bodies can be found by clicking the links above.