I realise that it was fatal to refer to the sociological theory of gatekeepers in a blog.  I knew it only by reference to the idea that in any organisation some people have disproportionate influence by acting as a point of intersection, both to people outside the organisation, but, more importantly, to those within.  I now discover that the idea stems from the social psychologist Kurt Lewin who published a study of the distribution of food in 1943 and that there have been multiple interpretations of the term ever since.