By Tim Donovan
Political Editor, BBC London
Hooliganism during some West Ham United matches at London's former Olympic stadium has cost the taxpayer more than £500,000 this year.
The figures were revealed by the London Legacy Development Corporation (LLDC), which runs the site - now called the London Stadium.
The LLDC's Lyn Garner said police and stewards had to be deployed because of the bad fan behaviour.
The comments were made during a London Assembly committee meeting.
Ms Garner said that West Ham's qualification for European competition required higher stewarding and security costs due to the additional games.