Primary position

This is a good point Oliver. Sadly, several of the most dangerous cyclists I have ever riden with have been cycle instructors. [...]

All the cycle instructors I know are very good, safe, and responsible riders. The people you know must be odd indeed. :)

While I totally take your point and don't want to question your judgement about what happened, it is worth mentioning that, while riding in the primary position is generally pretty safe, it can appear more 'dangerous' to onlookers. This is obviously a reflection of the method of making risk more conspicuous.

Before anybody starts to try to guess which instructors I am talking about, please note that I do know some who are not on this forum or from London. I am also in no way saying that all cycle instructors are dangerous riders, I am talking about a minority.

Hell yeah, Dan, don't worry, we all know that you're really talking about all the roads between London and Cumbria getting Scobled. ;P

Primary position is a very useful tool that I can use when the circumstances mean that it will put me in a safer position. If there is space for me to safely be out of the way on the left I will do so instead.

Just be careful to let your riding be guided by your risk assessment of traffic conditions. There is no reason to express an unequivocal preference for one position over the other. This aspect of cycle training really just seeks to correct people's tendency to think that the secondary position is somehow inherently the preferential position. That may not be what you meant, but that's how it comes across.

Like all safe cycling theories, they must only be used where appropriate rather than as a rule.

Yes, and remember that it's not only a 'safe cycling theory'. It's really about making riding more enjoyable, in the way in which greater skill generally makes things enjoyable. Most people, for instance, tend to (vastly) overestimate the risk to them when they move in traffic, partly from knowing very little about traffic. Giving them a little more knowledge can really help make their riding more enjoyable. There are other aspects to it, too.

(Small rant: Many people (not you) are obsessed with the concept of 'safety'. This is a reductionist bogeyman that's surprisingly hard to explain. In the grand scheme of things, for cycling, the importance of 'safety' as an action-guiding concept is relatively small. It is extraordinarily important in dangerous occupations, such as working in a shipyard or a coal mine, but for cycling, which is not 'dangerous', its pre-eminence really results from a combination of enhancing factors that are not immediately obvious--e.g., a sense of social abandonment that people tend to experience from feeling like a minority in the UK's predominantly non-cycling culture (which is changing fast), i.e. a feeling of a lack of the safety that one can normally rely on from social consideration. Cyclists often feel discriminated against. This flows into the idea of a lack of safety from the mere physical experience of interacting with people who drive cars and accounts for much of the well-known gap between the perception of 'danger' and actual risk (the perception is usually higher, often much higher, and in some people positively hysterical).

Quite often, the perception is additionally reinforced by people doing something for which they are not skilled enough and which they expect they should be able to do very easily and without any effort on their part, because 'it's just like riding a bike'. There are, of course, a number of different cycling skills. For instance, quite a few of the best bike handlers I know, strong riders who will happily ride 150 miles very fast, are very scared of motor traffic and interact with it very badly. By contrast, I'm a rubbish bike handler, but I've never had a problem riding in traffic. Some people are neither good bike handlers, nor good in traffic.

So, 'safety' is something that tends to crowd out other important topics to consider. Don't get me wrong, there are still far too many collisions, but pegging them only to the concept of 'safety' is a red herring. We'll be far more effective at reducing them if we think about this with a broader picture in mind.)