 Earthworks were underway and the tunnel near Elstree South station and the viaduct for Brockley Hill station had been partly constructed when the start of World War II caused works to cease.Work did not restart immediately after the war as there were stronger demands on funds for works elsewhere including the reconstruction of many damaged stations and the extensions of the Central line.After the introduction of Metropolitan Green Belt the Elstree and Bushey areas were protected against development, so the need for new stations to serve new residential developments in the area disappeared and the project was cancelled in 1950.