 With the hostile Metropolitan Railway controlling the GCR 's only approach to London through Quainton Road and Aylesbury , GCR General Manager William Pollitt decided to create a link with the Great Western Railway to create a second route into London which bypassed all MR property . In 1899 the Great Western and Great Central Joint Railway began construction of a new line , commonly known as the Alternative Route , to link the GWR 's existing station at Princes Risborough to the new Great Central line . The line ran from Princes Risborough north to meet the Great Central at Grendon Underwood , about three miles ( 5 km ) north of Quainton Road , thus bypassing Quainton Road altogether . Although formally an independent company , in practice the new line was operated as a part of the Great Central Railway . The new route opened in 1906 , and a substantial part of the GCR 's traffic to and from London was diverted onto the Alternative Route , damaging the profitability of the MR 's railway operations . 
