It was 19mph, that's not exactly head down busting a gut. I am not a fan of this "you must slow down to a suitable speed to avoid morons who might do something stupid in front of you" attitude that seems to be getting more and more common on here. What is a suitable speed? In
@buggi 's example above the only safe thing to do was to stop, get off and walk past the lorry, or go at less than walking speed. Who in reality does that? This is the real world and other road users should take care when using the road, but to expect everyone to come to an almost stop when using a cycle lane in this instance just will not happen. Personally I don't filter nor use cycle lanes, too dangerous!
I do not cycle thinking about the "what if" scenarios, if I did I wouldn't get on my bike, car or motorcycle. I have to trust that other people take as much reasonable care as I do.