It's a job that can only be done under the cover of darkness.
As night falls, the bat hunters make their way amongst the gravestones of Guestwick Church in Norfolk.
The creaking door opens. Inside is the pitch black, deserted church and the team start to set up their specialist gear.
Infrared and thermal cameras are carefully positioned, and audio detectors are set to bat friendly frequencies.
The bats soon begin to emerge, darting and swooping up and down the aisles, the amplified sounds of their bat chatter filling the historic building.
