"Tom Anderson" wrote

No, Crossrail should stop at Slough, and concentrate on being an
affordable and effective suburban railway, and not a pie-in-the-sky all
things to all people scheme.

Crossrail will go to Maidenhead, Heathrow, Shenfield, and Abbey Wood. Any
strong pressure to change any of these destinations is more likely to mean
that Crossrail doesn't happen at all than that changes will be made.
Subsequent add-ons are possible - Reading is the obvious one, so that diesel
trains out of Paddington can be eliminated from the Relief Lines, while the
Main Lines can become a totally 125 mph railway. Gravesend is a long shot,
but may be needed for (and financed by) development in the Thames Gateway.
Another destination west of Paddington would be nice, but no-one has come up
with any convincing case. Richmond - Kingston did not attract universal
support. Amersham - Aylesbury would be nice, so that the Met line can
concentrate on Uxbridge and Watford, while the fast lines beyond
Harrow-on-the-Hill would become single use by Crossrail, and electrified at
25 kV OHLE. But traffic density is insufficient to generate a business case.
More trains can't be pushed down the GWML - there's not teh demand, and
capacity is needed for freight west of Acton Yard. So I think we're stuck
with the Westbourne Park reversing sidings.

Peter