Police officers will patrol train station platforms

Almost 400 extra community support officers will be deployed in specialist units, alongside police officers, to target violence and harassment.

They will patrol on buses and at train stations, especially at school leaving times, to deter anti-social behaviour.

Bexleyheath in south-east London was the first place to be assigned a team.

Vulnerable travellers

The initiative has been funded by London mayor Ken Livingstone who maintains that having more uniformed officers is key to deterring criminals and reassuring passengers

Mr Livingstone said: "Over the coming months, 378 police community support officers will be introduced on to the transport system in 21 outer London boroughs.

"They will form a highly visible policing presence on our transport network, provide reassurance and make public transport safer."

Ian Johnston, Chief Constable of the British Transport Police, said the new teams would be "especially helpful" during the post-school rush.

He said: "From experience we know that as well as being especially vulnerable to crime, large numbers of young people travelling in groups can be intimidating for other passengers."