In article ,
Alistair Bell wrote:

I must be missing something. How exactly is anyone going to get from
T123 to T4 then? Currently the official way to transfer is HEX -- and
in that direction you'd have to change at Hatton Cross to get the
tube. It's pretty much a guarantee that TWO changes of train to get
from Padd to T4 is a non-starter.

I'd have to guess that they decided splitting the trains would take
too long (probably right) and they'll run alternate trains to each
destination. I can't believe for a moment that they'll close T4 HEX,
and I also find it hard to believe that they'd switch it to a shuttle
from T123, for the simple reason that people travelling to Heathrow
often have a LOT of luggage, and a change of train just isn't
acceptable.

I share your puzzlement about how T4 will be served by HEX after T5 opens,
but the details have yet to be announced. My expectation is that it might
indeed be a shuttle between T123 and T4. Passenger flow to T5 will need
more than a half hourly service.

If I were Heathrow Express, I'd run the slow service to T123 only
until T5 opens,

(which is the current plan)

simply because the (idiotic) single line to T4 can't
cope with it -- but after T5 opens, split both the express and slow
services 50/50 between T4 and T5.

I am not sure this will be possible, as there are no plans to double the
line to T4. The longer term plan is to run both HEX and Heathrow Connect
stoppers at 4tph each, with Crossrail and/or Airtrack taking over the
Heathrow Connect paths if they happen. It now appears that the premium HEX
service will continue independently of Crossrail/Airtrack.

As and when Crossrail happens, that's probably all T5 (assuming the line
to T5 is double-track).

The line to T5 will be double from the outset. T5 will have 2 platforms
initially for HEX/HC, with provision for a further 2 additional platforms
later.

David