Ye gods, I've started barking orders at random cyclists now...
I often cycle down this road
http://g.co/maps/2sukt Occasionally you get a car driver who is aggressive and wants to squeeze you to get past (and it is a dangerous squeeze, trust me, and they usually do it at speed). So I've taken to riding smack down the middle, much to their ire. The poor dears are delayed by all of ten seconds, usually. It is not a long road.
Today a white van was inches from my back wheel, revving particularly aggressively. At the same time another cyclist was overtaking me on the right side of the road. Quite a lot of cyclists, at this point, dive submissively for the gutter in order to allow cars and vans to squeeze past, and before I knew it I'd shouted 'Don't let him past, there's not enough room!' at the cyclist who was overtaking me. He didn't acknowledge I'd said anything (probably thought I was some loony, giving orders to strangers, this is London after all), but he did stay on the right side of the road, and I stayed on the left not far behind him, so the van driver had no chance of bullying his way past with both of us blocking his way.