Management of the joint line was to be in alternate periods of five years by the two co-owners, the first five-year term being that of the Metropolitan.[4] After establishment of the MGCJR, new stations were opened at Sandy Lodge in 1910, and at North Harrow in 1915.[5]Aylesbury station was leased jointly to the MGCJR and the GWGCJR from 1907.[5]
The branch to Watford from Rickmansworth was authorised under an Act of Parliament obtained by the Metropolitan on 7 August 1912, but was a MGCJR project. Purchase of land began in 1914, but the First World War held up further progress, and the first contract for construction was not placed until December 1922.[4]
The route north of Aylesbury was closed to passenger trains in September 1966.[7] The railway line and stations are used today by Transport for London's Metropolitan line as far as Amersham, and Chiltern Railways provides a service from Marylebone as far as Aylesbury Vale Parkway station, opened on 15 December 2008, north of Aylesbury, about a four-minute journey.