I think that this story may have come from a Rip Van Winkle at the BBC suddenly waking up and discovering the similar story [which was very true and authenticated] relating to a super duper new crime reduction squad in Merseyside that was looking at these craft quite a few weeks ago.
In that instance various US precedents [Los Angeles and Massachusetts if I recall correctly] were mentioned as 'proof' that the concept was proven. As it turned out both quoted operations proved to have even scared the FAA to death and were halted. One was over LA and the other at low level over a crowd of motorcyclists in the middle of nowhere.
There are some 'twin' engine UAVs around [most I have seen are conventional twin tractor monoplane in layout] but it is early days in their development and it may be the assymetrics of an engine failing will be even worse than a single engine failure when the pilot cannot feel the beast slewing around.