Ah ! Bless you all! Everything said so far applies. Over the years I gave a few lectures to interested people, but it was not a basic requirement of my job, however, because I knew my subject I was able to do it with a bit of success. Years later I started going to Folk Clubs and naturally became involved and gave a performance, albeit to only 20/30 people, and I was a bag of nerves. So, yes, know your subject as well as possible!!!