[Crossposted to uk.railway and uk.transport.london]

Could anyone enlighten me as to whether the LU portion of a Network Card
discount National Rail ticket can be used before 10am?

The particular scenario is that I buy an Off-Peak Return (SVR) from
Cambridge (CBG) to Heathrow Underground (ZHJ), discounted with a Network
Railcard.

On the return leg of the journey, I wish to leave Heathrow Underground
at 09:30, say. As far as I was aware, this wouldn't be allowed, since
Network Card discounted tickets aren't valid for travel before 10am.

But the NRE Journey Planner is happy to offer me the Network Card
discounted fare as long as the connecting train from Kings Cross doesn't
depart before 10am - i.e. the Journey Planner seems to think the "not
before 10am" restriction applies only to the National Rail portion of
the journey, and not to the LU section.

Is the Journey Planner correct? It would be useful to me on occasion if
this were the case, but I have a suspicion that maybe this is just a bug
in the Journey Planner.

Anyone know the answer?

Cheers,

-roy