A very good point. The authorities/police don't nick phone users, motorway lane lurkers, zig-zag line pedestrian crossing parkers, etc. etc. Are they really going to hang around long enough to see if your running engine is 'unreasonable', then do all the form filling for a prosecution? I don't think so. And what about a portable generator?
2015 2.2 CDTi SENav 163ps manual 4x4 in Carbon Flash with 19\" alloy spare towing a Bailey Unicorn III Madrid @ 1500kg.