'When is it permitted to cross solid white lines in the centre of the road ?' was a standard question in the verbal part of the driving test when I took mine (admittedly 18 years ago...)
I wouldn't be surprised if it's a standard question in the theory part of the current test ?
So there should be no excuse for not understanding it.
The learn-it-by-heart-this-is-a-question-they're-bound-to-ask answers when I passed were something like
- if you're turning right into a side road or driveway, etc
- if forced to because the road is blocked by parked cars or other obstacle like roadworks
- if directed to by a police officer or other person directing traffic
- to pass a pedestrian, horserider or bicycle : but there was no specification of them doing less than this 10mph speed at the time...
I expect in practice what's happening is just the 'I've got to get past, otherwise they'll get in my way' blinkered mentality of some drivers, which applies to cycles, but also to L-drivers, milkfloats, etc
It really p*sses me off on the bike when some fool insists on passing me, just to get in my way.
But it isn't just bikes - years ago I sat with a girlfriend, giving her extra driving lessons, and I was appalled at the way some people used to squeeze past in the most ridiculous, inappropriate or just plain dangerous places
- some people saw a Learner as someone needing more room, someone who you either treated with greater courtesy, or gave a wide berth to, depending on your viewpoint
- others saw a Learner as someone who just had to be passed as soon as possible, 'otherwise they'll get in my way...'
This sort of person passes you
- regardless of whether it's safe or sensible, they have to get past
- even if they're travelling at the same speed as you or even slightly faster, so they accellerate past you and then slow down in front of you and get in your way
- even if they actually want to turn left in 50yds, so they'll pass you and immediately brake and turn-off
- even if you're coming up to a red traffic light, they'll pass you and then immediately brake in front of you
- even if there's a sleeping policemen in the road ahead, so they'll accellerate past and then brake hard in front of you