FROM THE RTA ( ' It is illegal to leave a child unattended in a vehicle in circumstances where the child may be placed in distress or their health is in danger.' )

Particular emphasis should be placed upon the last part which is where the discretion becomes relevant. My children are neither placed in distress nor is their health in danger; in fact my arguement is that to remove them from the car under certain circumstances (such as when they are asleep and I am only a short distance for a minimal amount of time) that would actually act to cause them distress and place their health in danger (in a busy carpark). Often the police aren't really up to date on the law either.