T.S. Cordiner wrote in
:

I am unsure exactly what the argument for the gateline staff is anyway

One very important function that gateline staff perform is letting out
passengers whose tickets refuse to open the gates. Almost every time I
go up to London, I find that somewhere during my travels around the
underground I'll encounter a station whose gates won't recognise my ticket,
either on entry or else on exit.

And we'll have no jokes about the effect of my magnetic personality on the
magnetic stripe on the ticket ;-)