The LNWR electric units were ordered by the London and North Western Railway for its suburban services in London. The first cars, made with Siemens equipment, arrived in 1914, and these were followed by two larger batches of units with Oerlikon equipment. The trains were formed into 3-car units, with first and third class accommodation in open saloons. Following the 1923 grouping and absorption of the line into the London, Midland and Scottish Railway (LMS), similar LMS electric units, but with accommodation in compartments, were purchased to run with the Oerlikon units in 1926 and 1932. The trains were all withdrawn by 1960.

The London and North Western Railway's inner-suburban network encompassed the lines from London Broad Street to Richmond and London Euston to Watford and branch lines such as Watford to Croxley Green. With links to the District Railway at Earl's Court and over the route to Richmond, and the Bakerloo line being extended over the Watford DC lines, the railway was electrified with 630 V DC fourth rails. The electricity was generated at the LNWR's power station in Stonebridge Park and a depot built at Croxley Green.

The first four electric multiple units used Siemens electrical equipment and were composed of a driving trailer third, composite trailer and driving motor third with four 250 horsepower (190 kW) traction motors. The trains seated 38 first and 138 third class passengers in open saloons. These entered service on the West London Line route between Willesden and Earl's Court in November 1914, although the LNWR had been operating services since May using stock borrowed from the District Railway.

The second batch of trains, 38 three-car sets and 5 spare motor cars, used Swiss Oerlikon equipment and was generally similar to the Siemens powered stock. The four traction motors were rated at 260 horsepower (190 kW) and these trains seated 33 first and 130 third class passengers. The third class accommodation was a mixture of longitudinal seating and seats arranged in facing bays in pairs on either side of the gangway. The first class accommodation (downgraded to third class at the beginning of the Second World War), occupied two of the three saloons into which the intermediate car was divided, one being for smokers and the centre saloon for non-smokers. The saloons were separated by swing doors with frosted glass or bevelled plain glass glazing, the latter having an etched LNWR script decorative monogram. The first class seating was in facing pairs arranged 2+1 on either side of the gangway, and the general ambience was Edwardian-luxurious, with mahogany panelling. Above the seats were glazed frames which displayed photographs of landscapes and towns served by the London and North Western Railway; these were retained to the end.

Glazing consisted of large fixed lights with two small outward-opening lights above a transom; some were top-hinged and others side-hinged to provide alternative ventilation. Entrance doors were single-leaf sliding, and hand operated.

For operation on the extension of the Bakerloo line, the LNWR and the London Electric Railway (LER) ordered new Watford Joint Stock, but were delayed by World War I, not arriving until 1920. The electrification of the line to Euston was completed in 1922 and a further 75 three-car Oerlikon units and 3 spare motor cars were received.

After the 1923 grouping, the LNWR became part of the London, Midland and Scottish Railway (LMS). In 1926 and 1932, further 3-car LMS electric units, similar to the LNWR electric units but with compartments, arrived to strengthen the London fleet.

The LMS numbers of the Siemens stock were: