Every driving examiner is different. Of course there could be circumstances where 36 in a 40 limit might well be seen as dangerously fast - parked cars, pedestrians, bicycles can all make a slower speed appropriate.
What you are expected to do is keep up with the traffic, without going over the limit of course. When you have passed your test, you will find that being 'stuck' behind someone at 36 in a 40 limit on an open road is very frustrating.
Driving examiners are of course aware that a learner driver is inexperienced and nervous and so may drive a little slower and hesitate a little more than experienced drivers. Although driving too slow during a driving test may be acceptable to a degree, there can be a point where it can become dangerous. Driving too slowly can result in drivers behind getting frustrated, impatient and will to take risks to overtake. To be honest, even examiners find persistent learners who drive to slowly an irritating and tedious test to conduct.
An example of driving too slowly during a driving test would be a clear and straight 30 mph road with little or no hazards where a learner may drive between 20 and 25 mph unnecessarily, not where hazards such as parked cars, cyclists or bends in the road may reduce the speed of a vehicle. Persistently and unnecessarily driving too slowly can result in a serious or over 3 minors within the same category which also equates to a serious mark.
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