The mayoral debates are on TV tonight (Picture: Getty/Shutterstock)
Sadiq Khan is fighting to be re-elected as Mayor of London.
In the City Hall elections due to take place on Thursday May 2, the Labour politician is battling with 12 other candidates.
Khan, as well as Conservative Susan Hall, the Greens’ Zoe Garbett and Lib Dem Rob Blackie, took part in a debate that will be broadcast on Thursday April 25 at 8pm, on BBC One.
The mayoral candidates clashed on the Met Police, violent crime, affordable homes and Ulez.
But what is the history of the role and how does the election work?
How is the Mayor of London elected?
The mayor is elected by a system called first-past-the-post. It means whichever candidate in the election receives the most number of votes wins.
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The mayor is the chief executive of the Greater London Authority and has powers over housing, transport, the environment, planning, policing and the economy.
Due to the sheer amount of votes in London elections, the results are counted electronically.
The votes will start to be counted on the day of the election, after polls close.
Ballot papers will be verified on Friday 3 May, and the votes counted on Saturday 4 May (Picture: Dan Kitwood/Getty Images)
Who elects the mayor of London?
People who live in the 32 London boroughs which make up the Greater London Authority area.
These include inner London areas, such as Camden, Greenwich, Hackney, the City of London, Hammersmith and Fulham, Islington, Kensington and Chelsea, Lambeth, Lewisham, Southwark, Tower Hamlets, Wandsworth and Westminster. And the outer London boroughs: Barking and Dagenham, Barnet, Bexley, Brent, Bromley, Croydon, Ealing, Enfield, Greenwich, Harrow, Havering, Hillingdon, Hounslow, Kingston upon Thames, Merton, Redbridge, Richmond upon Thames, Sutton, and Waltham Forest.
The mayor of London is directly elected. But some mayors are appointed by fellow politicians.
So they stand to be elected as, say, a member of a local council and are elected to do the job of mayor by other members of the council.
Sadiq Khan is running for re-election this year (Picture: Stefan Rousseau/PA Wire)
How many times can a mayor be elected?
There are usually no limits on how many terms a mayor can stand for office, provided they continue to get public support and are willing to put themselves up for election.
Sadiq Khan is currently standing for an unprecedented third term as mayor.
How long is London mayor term?
When a person is elected to be mayor of London , they serve a fixed term of four years.
When was Boris Johnson elected mayor of London?
Boris Johnson served as mayor of London for eight years, from 2008 to 2016.
He stood down as MP for Henley to battle Labour’s Ken Livingstone for the top job at City Hall.
Whilst Mayor of London, Boris Johnson oversaw the introduction of the cycle hire scheme (Picture: AP)
Johnson was mayor when London hosted the 2012 Olympic Games and during the 2011 riots. He oversaw the introduction of the cycle hire scheme, new Routemaster bus routes and the Thames cable car.
He faced criticism for repeatedly championing the doomed Garden Bridge project, which was never built but cost £43m.
Who was the first elected mayor of London?
The first ever person to be elected London Mayor was Ken Livingstone.
The position was created after a pledge for a referendum on whether to have a directly-elected mayor for the city was included in former Labour Prime Minister Tony Blair’s 1997 election manifesto.
Ken Livingstone introduced the congestion charge, the Oyster card system and articulated buses (Picture: PA)
Some 72% of Londoners voted yes to having a mayor in 1998.
Livingstone, who had previously served as head of the Greater London Council, was elected as an independent in 2000 as Blair did not want him as the official candidate. He stood as Labour’s candidate in 2004 and was re-elected.
Dubbed ‘Red Ken’, Livingstone was on the hard left of his party and introduced the congestion charge, the Oyster card system and articulated buses.
He was also mayor during the 2005 terror attacks on the city and was a key figure in London winning the bid for the 2012 London Olympics.