"D DB 90001" wrote

But this still wouldn't be an ideal outcome, Oxford already has fast
services calling at Reading and Slough only, and passengers for
intermediate stations would need to change at Reading, so you might as
well terminate the service at Reading, but this would reduce the tph
from Oxford to Paddington from 4 to 2. Incidently the current Oxford
fast services are commonly 165s or 166s anyway so there are already 2
paths an hour for 90mph stock, whether there is any room for more than
that is debateable.

We're looking 8 years ahead, as Crossrail won't open before 2017. While
Crossrail trains won't convey passengers from London beyond Maidenhead, or
perhaps Twyford, it should be worth running them through to Reading, to
connect from intermediate stations into trains running further west, and to
save having to run dmus on the Relief Lines. Intermediate stations Tilehurst
to Cholsey, also Appleford to Radley, would lose their off-peak through
trains to Paddington, though this wouldn't be much of a loss, as passengers
mostly change at Reading on to a fast. In the peaks there could well be
trains from Oxford or Didcot which stop to Reading, then run fast to
Paddington (and these should be 125 mph stock - IEP anyone?

Crossrail trains shouldn't be all stations west of Paddington. It probably
wouldn't be too much of a loss if there were no through trains to Bourne End
or Henley - many passengers would be able to get a through train from a
central or east London Crossrail station to Maidenhead or Twyford, so they
would be saved the Paddington interchange at the expense of a change at
Maidenhead or Twyford.

Peter