"Jamie Thompson" wrote

...another great reason to have the Chiltern line to Princes
Riseborough as the 2nd western branch of Crossrail to free capacity
into Marylebone for more Birmingham and Aylesbury via Amersham
services I say

An early Crossrail proposal involved Crossrauil taking over the Chiltern Met
Line and the Met's Amersham and Chesham services, leaving the Met with
Uxbridge and Watford, and leaving Marylebone with the Chiltern Joint Line.

IMHO there is a case for the Croxley Link to include a half-hourly service
from Watford Junction via Rickmansworth to Chesham or Amersham.

Peter