Found this interesting whilst creating some screencaps for this episode - Ben's phone - the one which received the Sonic Fence breach warning - has no dial out capabilities:
Surely this can't be a prop error - probably just an indication that the phone is purely a warning receiver - perhaps it's not only the fence which is configured to send warnings to Ben, but other things too. The button in the Swan not being pressed, for instance - does he know hat Des missed the timer?
Just thought this was interesting. Well
fairly interesting, in comparison to the rest of this mega episode!