Cultsdave: Very easy to use a dashcam hard wire kit that plugs into fuse box live, most decent cameras detect movement/knocks to car body when car is locked up/stationary and will switch itself on for a predetermined time to start recording possible incident. There’s plenty of choice with dash cams small enough to fit behind rear view mirror and if you can wire a plug you can install a hard wire kit and hide the wires behind dash, a-pillar trims and headlining very easy.
Some cheap eBay special dash cams can cause digital radio interference and may need a ferrite choke placed as close as possible to the camera, apart from that there’s no practical reason for not having one