About Calculating overtaking distance: the 60-formula and the blind spot: which statement is WRONG?
The sequence is three steps: first the interior mirror, then the left exterior mirror, AND THEN over your left shoulder — only that last step covers the blind spot no mirror shows (trap: final check step skipped).
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.
On the motorway overtaking is always safe, so the manoeuvre may take as long as you like.
At 80 km/h and a leader at 25 km/h the overtaking distance is 87 metres; at 80 km/h and a leader at 60 km/h (a smaller difference) the overtaking distance is 240 metres.
Explanation
trap: 'mostly safe' confused with 'no limit'. Book p.147 - even on the motorway the manoeuvre may not take longer than necessary, and you may not exceed the maximum speed