But then couldn't the examiner give the learner their license ? How do police have their say in this ?
(IANADrivingExaminer, but, at a guess...) the incomplete test likely is the hurdle. Say that the examiner hasn't yet had the examinee perform the [reversing round the corner/parallel parking/three-point turnchoose one, according to whatever arcane rituals the examiner must observe
], or the emergency stop, or perhaps even just the mandatory full half an hour of freestyle driving required to pick up proper MSMing, then despite having done well (and not failed on any (significant) points) so far, the letter of the rules must class the test exactly the same as a test being prematurely aborted due to the learner actually crashing into something or committing enough demerits as to cause the tester to call the whole thing to an immediately failed halt and perhaps even assume control themselves in extreme circumstances.
The phenomenon of an actively-in-examination car being pulled over for a passive
traffic offence (ANPR cameras capturing details that the national database red-flags, as likely occured in this case) is going to be far more rare than being halted for an active offence being observed. It is also something the examiner could not detect (without running their own DVLA check whilst visually assessing the vehicle for mechanical defects before even starting). If the rules say that a (proven legitimate) police stop is an auto-fail, then an auto-fail it would have to be.
Also we've only had a handful of years without Tax Disks to check (a decent indication that the vehicle has had at least recent
MOT and Proof Of Insurance in order to be able to get to the point lf paying the tax), so again it is a fairly new problem that a car might be on the road with only specially equipped police and DVLA vehicles capable of uncovering any easily accidental failure to properly reinsure the vehicle, and the old methods just haven't had time to catch many "innocent testee" cases to force review of procedure in this case to at least give leave to grant discretionary passes in these circumstances, pending discussion by the Examiners' Council or whatever body might exist with such authority.
(W.R.T. the instructor able to instruct whilst banned: with the possible exception of a short period during a fuel crisis, a few decades ago, I think Learners on a provisional licence need to be accompanied by someone who holds a valid
(and at least three years old?) full licence. I don't know what the status is of a currently-over-pointed licence, but I'm doubtful it'd be considered properly valid if it can't be driven on. And it sounds like a lower limit of (non-disqualifying) points disbars a person from acting as a registered instructor. Maybe it lets him 'instruct' much as a parent or family friend might do, but then there's murky waters of a different kind. Would have to use the learner's own(/family) car, probably, as specific Instructor Insurance for a Driving School vehicle (dual-controls and all) would probably be inaccessable.)
(Ninja2: From my own reading of the article, the Instructor had to be brought to
the stopped vehicle (from the Test Centre, and the Examiner at least would have needed to get a lift back there anyway). And, good catch: the Instructor doesn't run the exam. They're usually only involved as far as being the "vehicle donor" for the test, and would be waiting at the Test Centre like a 1950s expectant father waiting outside the Labour Ward for news of how his wife and imminent child eventually manage. Though they'd perhaps be at least more used to it than the fathers who had arrived with their daughters in the family car to go through the exact zame process - in both types of instance!)