During the late 1960s it became clear that the number of people using the line had not become as high as people thought that it would. Not a lot of new development was allowed because the land was now Green Belt land. The number of people using the line peaked in 1971, and it was still only 650 people every day. This meant that the line did not make very much money. London Underground tried to close the whole line in 1980, but they were not able to. Instead, fewer trains were run on the line and they also closed Blake Hall tube station on Sundays.