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.
"Evacuate the area" the senior official said. I kept muttering back; "I'm a Cambridge University lecturer - there is nothing harmful in there....". But, to no avail. Eventually (and we are talking 30 mins here). They decided to remove the bag and investigate. I was not allowed to do more than open the zips. I stood back. They found the metal cup and in it were my cycling gloves, a small pump and an inner tube. The senior officer told me not to travel with that pump again (a small all plastic pump). But, the pump wasn't the problem. On rescanning the problem remained. It was my long valve inner tube. Apparently it looks just like a DETONATOR. It is a real shame that the staff can't look and listen a bit. This isn't security, it is a stressful farce. Still shaking some 30 mins later.