Bletchleyite
Veteran Member
This can't happen as described. Barriers cannot be closed if there is no staff member monitoring, either in person or via an intercom.
In an extreme case such as the staff member being attacked or taken suddenly ill, there is a red plunger (usually behind a break glass panel) which when operated opens all the gates.
It certainly has happened to me more than once. Staff were meant to be monitoring it remotely but weren't. I ended up barging through.
I've had the same on a LU station years ago and the emergency plunger was broken!