When you may, may not, and how to do it safely
Before you overtake: clear sight, enough distance from oncoming traffic, room to return without crowding the car you passed. Miss any one of these and you don't overtake. Hesitation is a signal to wait, not to accelerate.
You may not overtake across a solid centre line, immediately before a pedestrian crossing, at a railway crossing without barriers, or where view is blocked by a bend or crest. The 'no overtaking' sign applies until the cancellation sign — not just to the next bend.
When overtaking a cyclist: leave at least 1.5 metres of side clearance at 50 km/h, more at higher speeds. A bus at a stop: leave room for the doors and for passengers who may run out in front. A stationary queue in the next lane: expect someone to suddenly open a car door.
The question isn't 'can I get past'. The question is: can I get back into my lane in time, without forcing anyone to brake? If you can't answer yes with confidence, don't overtake.
A crest can hide a whole camper convoy. The marked no-overtaking stretch includes the crest — the solid centre line applies even where it looks unnecessary. Wait until the descent begins; then you have full sight.
You're at 90 km/h behind a car doing 60. The road is straight, but a crest is 200 metres ahead. Think: will you get past and back before the crest? No. Wait. Crests are one of the three biggest fatal-crash risks in overtaking.