In message , Roy Badami
writes
Oh, sorry, NR tickets to London Thameslink were never valid on the
Moorgate branch anyway, so I don't understand why your ticket would
open the barriers at St Pancras or Moorgate.

Are you sure about that? I have a vague memory that they were valid to
Barbican and Moorgate until that branch was closed, but I could be
wrong.

I suspect the reason why the tickets open underground barriers at places
like St.Pancras and London Bridge is that when the through London
service is interrupted (nearly every evening and all weekend for the
last couple of years) these tickets are explicitly valid via underground
service such as the Northern Line. I have always found them to work the
relevant underground barriers at such times, and suspect that the
barrier software isn't clever enough to know the details of the times
when the Thameslink blockade is in place, so they may well be valid at
all times of day.

--
Clive Page