FL
You know as well as I do that a Constable is responsible for his own actions and decisions. 'Supervisor' functions are limited in that decision making process. The Police are not like the forces in that respect. I cannot see any role for a supervisor in this, or any other minor incident. Because that is what it is.
There is a difference between saying 'I don't think' there was a reason for requiring a test, and the conclusive statements made by some that the officer did not have a reason.
In the absence of facts I cannot say either way, nor can anyone else. You may be right that there was no smell of alcohol. Having said that, you could be wrong.
Having met a fair few aircraft on arrival, the smell of alcohol when the doors are opened can be strong, thoughout the aircraft. So in fact there may have been that smell. In that case, the rather unscientific 'nose in the mouth test' would have been inappropriate, but a breath test would be.
Referring back to something you were involved in, some 12 hours after drinking it is possible to be 6 times over the limit. So it is possible that someone could have been over the limit.
Obviously they were not, but that is the object of a breath test, to show one way or the other.
Astradome.
It is not a matter of being unfit, it is being above a prescribed limit.
That limit, as FL points out is very low. Therefore the reasonable grounds and the factors looked for would be correspondingly lower. You could be right, and they could have been lacking, alternatively they could have had very good grounds, just because they don't make those grounds public does not mean they don't exist.
The Force Policy is probably based around confidentiality as far as the person(s) complained of. Also, harsh as it sounds it really is no one else’s business