The spirit of a male was 'seen' in the room by one of the Bovington staff who had also come forward and shown himself to one of the Mediums on the investigation.  It suddenly turned very dark in the corner by the fire escape. Clear enough to the naked eye, but not picked up on infra-red.  The object appears on cue just after Martin speaks, and is interestingly heading in the direction of the Staff member, who collapsed with exhaustion after this vigil!

I'm ruling out dust as it was moving too fast. But still could be an insect!