Ballot probe ordered
Election bosses are investigating allegations that polling station staff in Croydon and Lambeth have spoilt ballot papers by writing on them.
London Elects said it was investigating what it described as an "isolated incident" in Lambeth where polling clerks had written what is thought to be the voting card numbers on 10 people's ballot papers.
A spokesman said any mark other than the voter's cross on the ballot paper made it invalid.
There are reports of a second, similar incident at a Croydon polling booth but London Elects was not able to confirm any details.
Around 5.5million registered voters are heading to the polls today to choose the city's mayor and 25 members of the London Assembly.