Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. During 1909-1922 the London and North Western Railway embarked on a project to electrify their London inner-suburban network, encompassing the lines from London Euston to Watford and the North London Railway from London Broad Street to Richmond, including branch lines such as Watford to Croxley Green, and links to what was to become the London Underground network. For this reason, the lines were electrified at 630 V DC fourth rail, the electricity being generated at the LNWR's power station in Stonebridge Park. The first electric passenger trains ran in 1914, on the West London Line route, but full services over the whole network did not commence until 1922, work having been delayed by the First World War. The London, Midland and Scottish Railway extended the network in 1927, by electrifying the branch to Rickmansworth. The LNWR placed orders for three-car electric multiple units from Metropolitan-Cammell in Birmingham. These units were formed Driving Motor Brake Third + Trailer Composite + Driving Trailer Brake Third. All the cars were open saloons and the electrical equipment was in a compartment behind the driving cab in the DMBT.