When I worked in a rural part of the county, we used to get reports of big cats quite frequently. A puma was reputed to wander the area over one particular summer. Investigations used to revolve around a phone call to the nearest zoo or animal sanctuary to see if any had escaped, followed by a quick drive round the nearest village. There were lots of reports but never a puma was found.
Essex Police seem to have called off their search for a lion.