The Watford Joint Tube Stock was built for the service to Watford along both the Bakerloo tube and the London North Western Railway (LNWR).

As a result, the cars were owned by both the Underground and the LNWR.

The cars were ordered in 1914, but construction was delayed by World War I.

For this to happen, there had to be a passageway by the switch compartment as required by the Board of Trade.

These cars were built with hinged doors to the passenger compartments, an arrangement that caused delays during station stops, as each door had to be manually checked before the train departed.