London Overground commuters are to get a month’s free travel after further delays to new trains were announced.
Transport for London (TfL) has had to borrow new trains to run on the 14-mile Gospel Oak to Barking Line.
New electric trains were due to run in 2018, but manufacturer Bombardier is still carrying out tests, according to TfL.
TfL’s Jon Fox said customers had “been waiting way too long for the trains they have been promised”.
The upgrade was due to a two-fold increase in demand since 2008, according to Network Rail.
TfL said the new electric trains were twice the size of the current diesel trains which should have been replaced in Spring 2018.
Mr Fox said: “Given the ongoing delays we are modifying three electric trains normally used elsewhere on the network and will put them into use on the Gospel Oak to Barking line until the new electric trains are here.”
BBC London’s Transport correspondent Tom Edwards said passengers on the Gospel Oak to Barking Line have been experiencing crowded trains and disruption for years.