This must be one of the worst pieces of advice ever dreamt up by these supposedly "advanced driver" organisations.
Back in the day it was nice and simple; mirror - signal - manoeuvre. Using indicators is and never was a substitute for looking properly. The lack of indicator usage has recently become something of a badge of honour because of this "advanced driver" endorsement. Or to put it another way, indicators have become something that only learners and wet-behind-the-ears drivers use.
Personally I am tired of arriving at T junctions or roundabouts and having to stop because there is a car coming from my right which is not indicating, so I have to assume it is going straight ahead across my path. Then the fecker turns left without indicating, into the street I am emerging from...... All because there was no-one behind him, and he possibly didn't see me as I was hidden by buildings on my approach to the junction. In the old days he would (or should) have been signalling a left turn on the approach, so once I had made sure that he was indeed slowing down and looking like he was turning, I could have emerged. That is just one example; I could go on all day about drivers not indicating.....
See, you've failed already. Its not mirror-signal-manoeuver , it's mirror-signal(if appropriate)-manoeuvre(if safe to do so). You've just failed your advanced driving course at the first junction.
The matter has been researched in depth since the late 1920's when The System was first devised and the evidence is quite conclusive. Drivers quickly tend to use indicating as a
substitute for looking. Mirror-signal-manoeuver quickly becomes signal-manoeuver if the drill isntnpractised. This is dangerous - running someone over hurts just as much when your indicators are winking.
Conversely, the advanced drill has been proven to enhance a drivers observation technique and the amount they actually see and take in. Then, as a last resort, if you're still unsure the mantra is (quite rudely), "if in doubt, knock one out, and look again", which if adhered to stringently counters every point you've just made.
Why do you think advanced drivers have less accidents and consequently pay lower insurance? Its not the cloth caps and picnic blankets. Indeed, police advanced (or old Class I like I was) drivers are the safest civilian drivers in the country, statistically less likely to be involved in a recordable or reportable incident than any other category.
Note - police standard is a higher qualification than civilian advanced. Police advanced is a months intensive training in excess of standard. Then you have to requalify again to get your advanced ticket in different classes of vehicle like vans, motorbikes, off road etc.
