 The MR management were horrified at the potential loss of income and restarted negotiations with the GCR , and a 1906 agreement meant that GCR traffic was shared between the old and new routes . Management of the shared route north of Harrow alternated every five years between the MR and GCR . ( A proposed link between Marylebone and the sub @-@ surface section of the Metropolitan Railway , which would have allowed GCR trains to run across London via the MR @-@ controlled Thames Tunnel and on to the south coast , was abandoned . ) The sharing arrangement meant through trains running from Chesham to Marylebone , as well as the MR terminus at Baker Street , and that the branch was worked by GCR trains as well as the ageing MR rolling stock . 
