In article ,
Rob wrote:
Im now wondering if my St Albans to London Thameslink Monthly ticket
is actually valid on some routes on the Underground, and if so what
they are. I tried asking at my local ticket office, but they didnt
seem to fully understand the question.

Yes, it will be valid on some routes as a result of interavailability
of NR and LUL tickets on certain routes.

NFM99 says the following, but note that this is out of date. As
Thameslink no longer serves Moorgate I suspect that the availability
to Moorgate will have been removed. Hopefully someone with access to
The Manual will be along shortly to report the current
interavailability, but for the moment, this is what I have:

National Rail tickets which include validity: between West Hamspstead
Thameslink and Moorgate/Elephant & Castle/London Bridge

are also valid by LU/DLR services: between West Hampstead and
Moorgate/London Bridge/Elephant & Castle by Jubilee, District and
Circle Lines (via Westminster) to Blackfriars, BUT NOT tickets 'FIRST
CAPITAL CONNECT ONLY', 'LDN NOT UNDERGROUND' or 'NOT UNDERGROUND'

-roy