Hate to sound cynical , did no one spot a lone bucket on the floor , with wires coming out of it ? Try leaving a bag alone at Heathrow ! 
  all to busy on the phone to actually realise what is going on around them . 
  Imagine having mobiles when the IRA was targetting the UK . bag  search on entry to stores .Only 40 years ago . 
  If they can scan your ticket , why not for explosives and drugs :-) 
  The technology  is here .