Over the next five weeks, Full Fact will be covering the London Mayoral election, providing coverage of the candidates' claims and what they really mean.
But to begin with - what exactly can the Mayor of London do?
The Mayor of London is part of the Greater London Authority (GLA), which was created by the Greater London Authority Act 1999. The Authority consists of both the Mayor and the London Assembly, which is tasked with overseeing the Mayor's activities.
The Mayor's powers can be undersood as split into general powers and specific powers. The general powers of the GLA were set out in the 1999 Act, which are excercisable by the Mayor acting on its behalf. The top line function of the Mayor is:
1. promoting economic development and wealth creation in Greater London;
2. promoting social development in Greater London;
3. promoting the improvement of the environment in Greater London.
These powers have been modified since the setting up of the GLA - the most major revision happening under the Greater London Authority Act 2007, relating mainly to housing, planning, waste and climate change.
The Greater London Authority was originally set up with four 'functional arms' which operate separately but whose 'stragegic directions' are set by the Mayor.
One of these - the London Development Agency - has since ceased to exist, while another - the Metropolitan Police Authority - is now the Mayor's Office for Policing and Crime (MOPC). The original and new bodies are listed below:
1) Transport for London (TfL)
2) Metropolitan Police Authority (MPA) - Now MOPC
3) London Development Agency (LDA) - Now defunct
4) London Fire and Emergency Planning Authority (LFEPA)
However, the way in which the Mayor's powers are excerxised is limited. The GLA has "few direct service and delivery powers" according to a GLA guidebook.
The Mayor can nevertheless appoint senior members of the functional bodies, although he or she cannot appoint the Metropolitan Police Commissioner. He or she may also sit as chair of TfL and the MOPC.
The other major power of the Mayor is to set the annual budget for the GLA, amounting to more than £12 billion.
Professor Tony Travers, Director of LSE London, also commented in 2010 that a significant part of the role is negotiating with central government for funding in order to improve London's infrastructure.
He or she also has "powers of direction" over the functional bodies, moreso now over the Metropolitan Police since the MOPC was set up. These powers are excercised via strategic plans which the Mayor is required to prepare and publish.
Limits to the Mayor's powers come through accountability checks set in place back when the GLA was created. The GLA outline the requirements upon the Mayor:
1. The Mayor is required to consult on his draft statutory strategies and must consider doing so before exercising the general powers of the Authority
2. The Mayor is required to publicise his strategies.
3. The Mayor and the Assembly are required to produce annual reports.
4. The Mayor is required to hold an annual 'State of London Debate'.
5. The Mayor and Assembly must hold two People's Question Time meetings per year, where members of the public may ask questions.
6. The Assembly is required to conduct its business in public
In addition, the Mayor is also accountable to the London Assembly, a body of 25 elected members who scrutinise the Mayor's strategies and promise delivery. Their sharpest power is to reject the Mayor's annual budget for the GLA, which they can only do with a two-thirds majority.
Beyond the powers set up in 1999, the 2007 GLA Act expanded the Mayor's powers.
On housing, the Mayor can produce a housing strategy that allows him or her to recommend the amount, type and location of new housing built in London.
This 'recommendation' is subject to guidance from the Secretary of State for Communities and Local Government. Local Authorities in London must generally conform to this strategy.
However, if the Mayor's plans are in contradiction with UK national policy, the Secretary of State can otherwise direct the Mayor's policy.
The 2007 Act also gives the Mayor powers over 'strategic' planninng which means he or she can, instead of a local planning authority, give permission to projects he or she considers important to London's development.
Here the Mayor's powers must be subject to hearings before the permissons can be enacted, and additional regulations apply under ordinanry planning legislation.
The Mayor can also set a 'waste management strategy' which can influence how people's rubbish is collected and disposed of.
There is, however, an additional limitation imposed upon the Mayor in relation to climate change. The Mayor must:
"consider the effects that any proposed excercise of its general power would have on climate change."
Further to this, the Mayor is required to publish a 'climate change mitigation and energy strategy' separately, as well as including these considerations in ordinary strategies.
The road ahead
Full Fact will be tracking the claims made by the major candidates in the London Mayoral election. The powers of the Mayor of London are limited, but the Mayor certainly exerts influence, in particular, over transport, planning, policing, fire protection, the environment and culture.