Night Tube services to begin on the Northern Line
Night Tube services will begin on the Charing Cross branch of the Northern Line later.
It follows the launch of 24-hour services on the Central, Victoria and Jubilee lines.
The Northern line becomes the latest line to switch to 24-hour operation since the Friday and Saturday night service launched on the Jubilee line in September.
Night Tube services will start on the Piccadilly Line on 16 December.
Transport for London (TfL) said there would be a train about every eight minutes between Morden and Camden Town and about every 15 minutes from Camden Town to High Barnet/Edgware.
Standard off-peak fares will be charged and Day Travelcards cover journeys made until 04:29 the next day.
TfL said nearly 1.5 million Night Tube journeys had been made on the Central, Victoria and Jubilee lines.
It said the service was cutting journey times by an average of 20 minutes, with some cut by more than an hour.
The Mayor of London Sadiq Khan said: "Londoners have really taken these new services to their hearts, with nearly 1.5 million journeys made already.
"The Night Tube is helping tens of thousands of passengers get safely to and from work or home from their evenings out every weekend, and it's great news that even more of the capital will be opened up with the addition of the Northern line tonight, and the Piccadilly line next month."