It also introduced the concept of a regular hourly service .
The new timetable concentrated on key points at Oxted , East Grinstead and the Ashurst - Groombridge - Birchden triangle .
East Grinstead also introduced the concept of a regular hourly service .
The new timetable concentrated on key points at Oxted , East Grinstead and the Ashurst - Groombridge - Birchden triangle .