Evacuate the area - the last words you want to hear at an airport?

Mega stress at Check-in at Heathrow Terminal 3. Got to x-ray machines and my bags were stopped. First one staff member was called to the computer display and then within 10 mins 6 security staff were gathered around it. I was then ask for a list of all the items in the bag. Eventually it transpired it was a metal cup and contents that had been identified as a BOMB.