About Calculating overtaking distance: the 60-formula and the blind spot: which statements are correct? (multiple answers possible)
The rule is stated generally: 'when overtaking pedestrians and cyclists, keep sufficient lateral distance (at least 1.5 metres)', with no restriction to motorways or high speed.
Before overtaking it is enough to check your interior mirror and left exterior mirror; checking over your shoulder is then no longer necessary.
Before overtaking you first look over your left shoulder and only then in the mirrors.
Right before overtaking, keep sufficient distance to the vehicle ahead (2-second rule), so it can see you coming clearly.
Explanation
The book's sequence starts with the interior mirror, not with the shoulder check (Book p.143).