Bit quick to jump on the old trainee there !
I heard that the trainee descended an aircraft after checking strips and radar. Unknown to him there was traffic directly underneath not co-ordinated in, with no strip, and had been relegated to a background track, and thus was invisible. Then the training box went u/s and it all got a bit close.
At least that's the story here at TC........anyone from the Great Level Capping centre care to comment?