The new line was to have been called the Fleet Line after the River Fleet, but the project was renamed for the occasion of Queen Elizabeth's 1977Silver Jubilee and because the original plans to go West towards Fleet Street had been shelved. The choice of grey for the tube map is presumed to represent silver.
The Jubilee line of 1979 was meant to be only the first phase of the project, but lack of funds meant the line stayed the same until the late 1990s. Phase 2 would have extended the line along Fleet Street to Aldwych and then across the River Thames to Lewisham.
Changes in land use, particularly the urban renewal of the Docklands area, meant the project to extend the line beyond Charing Cross changed considerably in the 1990s. The Jubilee Line Extension, opened in three stages in 1999, split from the existing line at Green Park, creating a one-station branch to Charing Cross which is now closed.