Honestly, there are people at the border whose entire job is to look for suspicious items. (It's not like the threat of a bomb attack in London is a purely hypothetical one, http://en.wikipedia.org/wiki/List_of_terrorist_incidents_in_... ). If you're gonna carry a suitcase full of weird-looking homemade electronics across the border, then yeah, you're probably gonna wind up answering some questions about 'em. In the end, they were correctly determined to be no threat and free to go with their drones.