Teepee wrote:
So coming up to a roundabout on a NSL road, you might be in 5th gear. Brake up to the roundabout and then, if clear, you can drop straight into (usually)second before accelerating away. If not clear, then stop and straight into 1st. Changing down a gear or 2 to go round a bend is completely different, and the correct gear for going round a bend should always be selected prior to entering the bend. So changing down a gear or two for a sharp bend prior to a roundabout is always appropriate.
I must admit, I have changed my style to this as a result of taking an IAM course, and did find that it took quite a bit of getting used to.
You describe pretty much what I have always done. Usually it's 5th to 3rd for your NSL roundabout example, 5th to 4th for a bend that merits a slowing-down, and 5th or 4th straight to 2nd for a corner such as a side road.
The trick being to do the single gear change just as you finish braking, and
before you turn into the hazard. (Changing gear late, when you're partway through the roundabout/corner, is not good for your car control or the balance of the vehicle.) With practice it makes for relaxing and rapid progress.
Going down through the gears is usually unnecessary unless you have a sequential gearbox. I think the "engine braking" thing came about because earlier cars had drum brakes that were prone to fade, so going down through the 'box saved the brakes and gave you a sporting chance of having some braking capability left at the end should you need it.
(Edit: removed erroneous phrase implying I was advocating left foot braking.)