"Andy" wrote

Actually, I don't know why 18 manages 12 car, but 19 is down as 8 car.
I've had longer trains that 8 coaches in platform 19. For example a
2+9 HST to Reading via Ascot during engineering work (and I think the
Eurostar connection HSTs also generally used 19); I think this went
via the Windsor reversible . The platform face for 19 goes all the way
to the end of the Eurostar platforms although it is very narrow at the
country end and it maybe that it was only checked for multiples of 4
coaches when it was surveyed.

Are you sure the HST was 2+9? AFAIK WR HSTs have never been longer than 2+8,
and the E* connection HSTs were also 2+8. A 2+8 HST is shorter (by about 1
coach) than a 12 car train of 20 metre stock (though as also posted, it
seems the platform can physically accommodate a 12-car SR emu,but the outer
end is non-compliant, presumably because it is too narrow).

Peter