 For the extension to Queen's Park, the LER supplemented the existing rolling stock with 14 new carriages ordered from Brush Traction and Leeds Forge Company plus spare Gate stock carriages from the GNP & BR. These carriages, the 1914 stock, were the first to have doors in the sides of the carriages as well as the ends. For the longer extension to Watford, the LER and the LNWR ordered 72 new carriages from the Metropolitan Railway Carriage and Wagon Company. Manufacture of this rolling stock was delayed by the war, and, while it was waiting for delivery, the Bakerloo Tube used spare 1915 stock carriages ordered for an unfinished extension of the CLR to Ealing Broadway and more spare Gate stock carriages from the GNP & BR. Delivery of the carriages for the Watford service, known as the Watford Joint stock because ownership was shared with the LNWR, began in 1920; they were painted in the LNWR's livery to distinguish them from trains operating only on the Bakerloo Tube's tracks.
