The night began in celebratory mood - but it later turned sour
The alcohol ban on London's transport system has started, after a night of partying on the Underground during which 17 people were arrested.
Six stations had to be closed as thousands of people gathered on the network in advance of the ban.
Passengers are now barred from having open containers of alcohol on the Underground, London buses, Docklands Light Railway and trams.
Union leaders have described Mayor Boris Johnson's policy as "half-baked".
The ban will not be enforced with extra policing - instead a "softly softly" approach is being used, where it is hoped the ban will be self-policed, in much the same way as the smoking ban.
"Notices, staff advice and announcements will make the alcohol ban clear," said a Transport for London (TfL) spokesman.
"If necessary, our staff can call on the support of 2,500 dedicated transport police and community support officers across the transport network."
But Bob Crow, of the Rail, Maritime and Transport (RMT) union said: "We will support any measure that will make our members' working lives safer and more pleasant, but the ban has been poorly thought through, is being implemented in haste and could put our members in greater danger."
On Saturday night, drinkers gathered on tube trains and station concourses hours before the ban came into effect.
The party, mostly on the Circle Line, was dubbed the Last Round on the Underground.
It had been widely advertised on social networking and other internet sites.
The party began in a celebratory mood, with many people in good spirits and anticipating a good night.
But four Underground drivers, three other staff members and two police officers were assaulted, when trouble flared.
Several trains were also damaged and withdrawn from service.
Police said what should have been a fun event came to an "unfortunate" end.
Liverpool Street Underground station was closed for several hours to ease overcrowding.
Other tube stations closed by police were Euston, Euston Square, Aldgate, Gloucester Road and Baker Street.
TfL's Director of Transport Policing and Enforcement, Jeroen Weimar, said the new policy on alcohol was a reasonable one.
"We are encouraging our passengers to show a bit more respect and to be more considerate and involve other people's views and other passengers' views as they make their journeys," he said.