 In the 1970s and 1980s decaying infrastructure and the withdrawal of subsidies brought the future of the line into doubt . As one of its last acts the Greater London Council paid for the replacement of two bridges on the line , allowing operations to continue . The centenary of the line in 1989 saw a renewal of interest and an upgrading of the trains between Chalfont & Latimer and London Marylebone station made commuting more practical , and usage of the line stabilised . The introduction of London Underground S Stock in 2010 led to the replacement of the shuttle service with half @-@ hourly through trains to and from London . 
