The future of Chesham services

A point on the last two postings, whilst LUL will timetable trains at very close headways on lines where the signaling will allow this sort of working. The Metropolitan is generally timed to run at 2.5" headways between Baker Street, Harrow and Uxbridge. This can be reduced to 2" from Baker Street during the peak but usually only occurs where the two trains will run on different lines from Wembley Park, and usually a fast before a slow. The Local lines between Harrow and Watford South can handle 3" headways, with 4" on to Watford. The Main lines north of Harrow will handle 4" to Amersham. Any less than those headways would mean trains running on restrictive aspects and the service would fail to maintain meet it's targets. Also the fact that defensive driving techniques are now pressed home, would see t/ops especially on the Chilterns not running at reduced speed and headways would be eroded.
The idea of tweaking the times of Amersham services is fraught with problems, in the same way as for the tweaking of the Chiltern times. This would require a complete recast of the Metropolitan WTT as the pathing of the Chiltern services are set by the pathing from of trains from Baker Street. This is currently constrained by the 12tph services to both Watford (6tph) and Uxbridge (6tph) and forming a 5" minute interval service to Harrow. This leaves paths for another 12tph in the timetable and 4 of these are currently used for the Amershams. If we take out another 2tph for the Semi to Amersham and the 6tph remaining would be available for other workings, though the constraints of platforming at Baker Street would generally make these unusable without altering the remaining service. The knock on from a major recast then goes onto affect the Circle, District, H&C, Piccadilly and Jubilee line services to some extent.
Ownership of the line may not be as clear cut as is believed the fact that this was a joint line between Harrow and Quainton Road the current split is really more of a convenience for both infrastructure operators and I am sure if you search it out there is documentation that gives Chiltern legal rights to operate over the Metropolitan.