these 41 high density sets operated the outer-suburban services from marylebone usually to destinations such as high wycombe, aylesbury and banbury which are on the chiltern main line and great central main line (now the london to aylesbury line). sometimes, these sets used to operate 8-12 car long expresses to nottingham victoria in the final years of the gcml. coincidentally, the 115 were under table 115 in the british rail timetable.