So how come it happens at Kings Cross late at night, onemember of staff, two trains, some 3 cars some 4?
Kings Cross, like various other stations that have been mentioned, has separate "a" and "b" sections for the platforms in the "Suburban" trainshed (Platforms 9 to 11), with separate feeds for their monitors...However, I don't
recall seeing two trains advertised on the same platform at the same time there.
And again, Kings Cross has more than one member of TOC Operations staff around late night, unlike Marylebone, where it's just one Dispatcher after a certain time.
The other issue is that, regardless of how many announcements you make and posters you put up, people
will manage to get on the wrong train, potentially resulting in them activating the emergency alarm when the train they've board goes through the station they wanted to alight at at 100mph!