Well that’s news to me after several years of driving trains in and out of several london terminals (admittedly not Euston, although I gather it’s the same there). The procedure is: you present yourself at the gate in full regalia, smile at the gateline staff and they let you through.
There’s a good reason for not using your staff travel pass in the machines - they break after five minutes.
Nobody ever asks you to show a pass - it’s simply unnecessary - that has been my experience literally thousands of times over the last few years. Staff get to know your face so security risk is minimal.
The
only occasion I have had an issue, I had followed the usual protocol, and was given an absolute verbal tongue lashing for not showing my pass by a member of gateline staff, who clearly had anger issues and a chip on their shoulder, in full view of passengers.
I had no choice but to declare myself unfit to drive, my outbound and return workings were cancelled as a result and my train sat idle, blocking a platform for a couple of hours.
I never saw him again after that.