That means being able to drive at up to the speed limit where road and traffic conditions permit.
Ah, there are the weasel words. In good weather, in suitably light traffic, where the nature of the road permits (visibility, curves etc), one one can drive to the speed limit. There is a very specific set of circumstances where one ought to reasobably be aimjng for the limit. At other times, one should drive appropriate to the conditions. Sod the driving test - when it goes wrong it's a judge or a coroner you need to be worrying about.
Not being nasty Brandane , I know you're a decent sort, but you must have some kind of stress management issue. What do you do when you're stuck behind a vehicle restricted to 50? How did you cope up until last year when lorries were restricted to 40 on single carriageway roads? What about caravans, that simply can not hustle along so fast? Or tractors? Or cyclists? What's wrong with exercising your driving skills to hang back and pass when safe? One shouldn't be getting frustrated - one should revel in the opportunity to demonstrate their superior driving skills at such moments.
But a tip - if this sort of thing really is causing you issues, leave home 5 minutes earlier.