Did you get a ticket?

I think the real trouble is that it's hard to convict on that. It's not like speeding, where you either are or you aren't, it's much harder to establish that you shouldn't be in the outside lane. I mean, it seems pretty clear in most cases, but the lack of a clearly defined boundary makes it very difficult in law. This ends up making it feel like a waste of time to law enforcement, both police and courts, because they could be doing things that will be more likely to have the intended outcome.

It's really annoying though, because advanced driver courses sometimes do define it: 10 seconds.

If you're not overtaking within 10 seconds, you should move over. Personally, I find it easier to estimate a 7 second distance by eye - 10 seconds is quite conservative.