Tim Woodall wrote:
...I know my Gold Card doesn't [work on the Underground], having
on one occasion had about 10 tries to get the barrier open before
realizing I'm using my gold card instead of the underground ticket I'd
bought.

I have the opposite "problem" to Tim. I have a Cambridge-London
Terminals Annual Gold Card. In my case the terminals are King's Cross
and Moorgate (plus Liverpool Street) which is handy as I can walk to
work from Moorgate.

The NFM handily states that such tickets are also valid by LU between
KX and Moorgate. And this is what I do every day, using my London
Terminals ticket to open the gates at KX and Moorgate.

So my "problem" is that whenever I exit the LU station at KX I have to
remember whether I have just travelled from Moorgate (in whch I need to
insert my Cambridge ticket in the gates) or whether I have travelled
from another LU station using my pre-pay Oyster.
About twice a month I absent-mindedly use my Cambridge ticket to leave
the station when I should have touched-out with my Oyster, leaving me
with an unresolved journey on the Oyster.

PauO