Is it time to start calling out bad cyclists?

undertaking people that you're not riding with is rarely ok. and you should at least say something before you do, like 'coming up the left' or 'on your inside' or something. i wouldn't expect people to check their left shoulder before moving in to the kurb if they were in the left hand lane already

Unless you're doing a bit of through and off, it's definitely not okay. I leave that space there for a reason and I might have to move into it - whether to avoid a pothole, drain cover or if I'm getting squeezed by traffic.

If someone's on the inside, I will lean on them if I have to. If they fall off, that's definitely their problem. (I'll stop to check they're okay and tell them how stupid they are though.)