London: The Night Tube was launched in the London Underground on Saturday -- almost three years since the plan was first announced.
Trains will now run on the Victoria and Central lines on Fridays and Saturdays between 12.30 am and 5.30am, the BBC reported.
London Underground expects 50,000 people to use the Night Tube each weekend, rising to 200,000 once all five lines are open.
The city's mayor, Sadiq Khan, was among those to board the first Victoria line service in the early hours of Saturday, the report said.
Khan spoke to passengers on the train, which departed from Brixton, south London, at 12.34 am.
"I'm really pleased that 100 days or so after becoming the mayor we've got that right," Khan said.
About 100 British Transport Police officers patrolled the network on the launch of the service.
Superintendent Chris Horton insisted there was "no reason" why passengers would not be as safe as during the day.
He said the force would focus on "being visible" and ensuring it was "able to intervene in places that are likely to see significant issues", the BBC said.
Plans for the Night Tube service were announced in November 2013, with Transport for London saying there was a "huge demand" due to passenger numbers on weekends soaring by 70 per cent since 2000.
The service was intended to begin in September 2015, but strikes over pay delayed the start by nearly another year, the BBC added.