 London Transport inherited a number of incompatible electric multiple units from the railway, including the 1927–33 multiple-unit compartment stock used on routes to Watford and Rickmansworth, and these were refurbished to form a uniform fleet and designated London Underground T Stock.In the 1950s, F Stock trains, with sliding doors under the control of the guard, were transferred from the District line; these mainly worked the semi-fast Harrow and Uxbridge services.A major rebuilding of the main line from Wembley Park to Amersham was planned in the 1930s but delayed by the war.