The all-night Tube was due to start on five lines at weekends last September, but was beset by delays amid a campaign of staff strike action.

But the breakthrough has followed acceptance of a pay deal by members of the two biggest Tube unions - Aslef and the Rail, Maritime and Transport.

The Transport Salaried Staffs Association and Unite have yet to accept the deal, but it is understood that TfL is pressing ahead with starting the Night Tube in August.

Part-time Tube drivers are currently being trained to deliver the new service and are expected to be ready for duty by the summer.