As stated above the IAM and ROSPA are there to promote safe riding however I know of 2 riders who failed their IAM test because of being too safe and not making progress when it was possible.
When I was working as an instructor (CBT & bike licence, not IAM) I worked out of Wembley and Northampton. If you filtered (on your test) in Northants, you would automatically fail. If you didnt filter in Wembley you would fail.
And I thought that was fair. The imperative to filter in Northampton was rarely that great, but in North London it was (and less risky than being at the back of a queue).
And that, for me, is what IAM, RoSPA and Bikesafe have reminded me these last few years. There are no rules of what is right, wrong, best, good nor bad. It's about thinking, thinking, and then thinking.
Got criticised on an IAM organised training day with Plod: For indicating when no one was there to see it. I argued that I was doing a right turn past a corner shop, someone could have been about to exit the shop, I couldnt see in, therefore the indicator was of potential value to them as they exited. Criticism withdrawn. No right, no wrong, just what are you doing and why.
I have heard rumours of an IAM group having a large number of riders turning up and riding at 42 mph everywhere. The argument seems to be running like this. Is it safe? Yes. It is safer than riding at 43? Probably. So what is the problem? If ultimate safety is the aim, then they would be teaching people how to polish their bikes in their garages and never ride them.
And if someone passes their IAM test never exceeding 42, how can the examiner say they are safe at greater speeds.
And riding at 42 mph could be considered dangerous on 'A' roads.
So it comes back to the first bit, about can you justify what you are doing. If you can justify to the examiner that you never exceeded 42 mph for good reason, you should pass. If your only reason was that is the speed you do, then I feel it is fair that you should not pass. Not fail, there is no failure involved in this scenario, just that you have not demonstrated that you are thinking, as well as the ability to be safe up to and at the national limit.
I have never heard of anyone being accused of not making progress if they rode up to the speed limits as appropriate.
PS What happens here is they all ping past the cars in the 30mph zone, then they get to the NSLA and hold everybody up whilst they wobble round the bends that country lanes contain. Slow? Yes. Safe? Errrr. Advanced Riding: Nooooooo.