In message , at 07:58:52 on Wed, 12 Sep
2018, Clive D.W. Feather remarked:
Heathrow Central to Kings Cross is 55 mins on the Tube, with no changes and
12 tph. Allow 2 mins waiting time, so 57 mins overall.

On Crossrail, it will be 31 mins to Farringdon, 6tph. Allowing 5 mins
waiting time, that's 36 mins. Then allow 10 mins to change to Thameslink,
and say 3 mins journey time to Kings Cross, so it's about 49 mins total. Is
it worth the hassle of changing trains with luggage, and up to triple the
fare, to save just eight minutes?

Depends on why you're going to Kings Cross. For a LNER train to Leeds,
yes there's a big difference. But for places like Welwyn, Huntingdon, or
Cambridge, you might as well change at Farringdon for a direct train.

Agreed for all but Cambridge, where it's perhaps useful to think of the
non-stop Cambridge services (the old Cruisers) as "LNER in waiting", and
if we are shaving minutes off here and there they will be preferable to
the semi-fast Thameslink trains which also take an age between arriving
at SPILL and departing Finsbury Park.

Why on earth would you get thameslink to KX? Get the H&S/Circle
line, there's a train every 2 or 3 minutes.

The change at Farringdon is likely to be much easier to Thameslink. Using
LU will make the change longer,

Why?

The two lines are in parallel platforms at this point; the southbound
Thameslink and westbound Circle effectively share a platform (albeit at
different heights).

There's not much in it, but the Crossrail station is beneath the new
Western[1] Ticket Hall, which also houses the southern extension of the
Thameslink platforms, and thus it's possible the walk to the tube
platforms will be longer. And possibly more awkward if we require
stepless.

[1] That's western in Crossrail parlance, it's obviously to the south of
the original tube/Thameslink ticket hall.
--
Roland Perry