The long-awaited Night Tube will finally begin this weekend - almost three years since the plan was first announced.
Trains will operate throughout the night from Friday on the Victoria line and parts of the Central line, with the Jubilee, Northern and Piccadilly lines to follow in the Autumn.
Around 100 British Transport Police will be on patrol across the network on Friday and Saturday nights.
London Underground estimates that 200,000 will use the Night Tube each weekend once all five lines have opened.
And experts estimate the Night Tube could be worth £77 million to London's economy by 2029.
Originally, the Night Tube was meant to begin its service from September 2015.
But a dispute with the rail unions delayed the project, while former mayor Boris Johnson was criticised for setting a start date before issues were resolved.
Current mayor Sadiq Khan has expressed his surprise at how long it took the issues to be resolved.
It's not me making a cheap point, but the previous mayor did announce the Night Tube start date on one occasion and that wasn't met, on a second occasion, that wasn't met, on a third occasion, that wasn't met, and then gave up.
Superintendent Chris Horton, the officer responsible for policing the Underground, has reassured the public there is "no reason" why passengers would not be as safe as they were 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".