[2] Running between Golders Green and Waterloo stations, it is operated by Metroline.

[3][4][5][6] In July 2016, Transport for London opened a public consultation on proposals for the route to be extended from West Hampstead to Golders Green as part of the Inner North West London Buses review.

[7] This took effect on 1 April 2017 with the route being extended to Golders Green and at the same was transferred from Metroline to London Sovereign.

[8][9] When next tendered, the contract to operate the route was re-awarded to Metroline with the handover occurring on 29 August 2020.

[10] Route 139 operates via these primary locations:[11] Media related to London Buses route 139 at Wikimedia Commons