A campaign to persuade Londoners to vote in the mayoral elections has been launched 100 days before polling.
People have to register by 16 April
The ballot for the Mayor of London and London Assembly representatives will be held on 1 May.
London Elects and the Electoral Commission are trying to encourage people to register to vote.
An official list of mayoral candidates will not be published until 2 April but the main parties have already announced their representatives.
Mark, an X-shaped figure, appeared outside City Hall to begin the campaign to encourage the London electorate to register.
It is estimated up to 1 in 5 Londoners, across all 33 boroughs, may not be registered to vote.
These include people who have moved house or are living in private rented accommodation, students, young people, and citizens of EU and Commonwealth countries.
The multi-media campaign will raise awareness of the need to be registered by 16 April.
The current mayor, Ken Livingstone, is standing for the Labour Party; Boris Johnson, MP for Henley, represents the Conservatives, and Brian Paddick, a former senior Metropolitan Police officer, is standing for the Liberal Democrats.
Sian Berry is the Green Party's candidate and London MEP Gerard Batten will represent UKIP.
Lindsey German represents Respect; Richard Barnbrook is standing for the British National Party; Chris Prior for the Stop Congestion Charge Party; and Winston McKenzie is standing as an Independent.