The LPTB was nationalised in 1948, and the reconstruction of the mainline railways was given priority over the maintenance of the Underground. In 1953 an unpainted aluminium train entered service on the District line, and this became the standard for new trains. In the early 1960s the Metropolitan line was electrified as far as Amersham, and steam locomotives no longer hauled passenger trains. The Victoria line, a new tube line across central London, opened in 1968–71 with trains driven automatically. In 1976 the isolated Northern City Line was taken over by British Rail and linked up with the mainline railway at Finsbury Park. In 1979 another new route, the Jubilee line, took over part of the Bakerloo line; it was extended through the Docklands to Stratford in 1999.