Or as an alternative theory, they didn't show him actually leave because it wasn't thought to be interesting or add to the story.
HM goes into diary room says I want to leave. BB says are you sure? HM says yes please. BB says OK please leave by the door to your left. Camera shows back of HM as he leaves the room.
Why waste airtime with it, if showing a surprise announcement to the HMs provides a more interesting bit of footage? Either way the news story has been told but one way has dull footage and the other a more interesting angle.
Its a dull explanation I know.

But it might be because the story played out in a rather mundane way.