The cockpit drill is a simple routine that you can learn very quickly, it takes next to no time to go through in the car and it keeps you safe by eliminating common causes of collisions.
As is normal with these routines, it looks quite involved with lots to remember, but the truth is that you'll go through the entire thing in about 10 to 15 seconds once you're used to it. Your instructor should give you plenty of practice at this. Actually, it should be done at the start of every lesson.
In reality, you'll probably have already been driving the car just before your driving test so you'll know most of this is done.
The Police system of Advanced Driving was the first fully complete system of driving and the cockpit drill learnt and routinely used by Police drivers is far more involved. It still takes no time to do in the car.
The simple drill outlined here is the one commonly used by Driving Instructors and is totally adequate for most drivers. Let's be honest, most drivers don't go through any form of safety routine when they enter a car, so any additional safety steps can only be a good thing. Most drivers have no idea of the number of collisions caused by missing out this vital step. Just a few seconds going through this routine can save you £1000's of pounds and an awful lot of inconvenience if you put your car out of action.
The basic routine can be memorised quickly by recalling the letters "DSSSM"