This paper analyses a lecture by an excellent teaching award winner professor of mathematics, given to high school mathematics teachers. The analysis is based upon two sources: (i) the lecture plan, as expressed in a series of 29 transparencies, prepared by the lecturer in advance; (ii) the actual implementation of the lecture, as transcribed from its video-taped record. Based on this analysis six principles for planning and giving a good lecture were developed. The paper provides the readers with full details of the content as well as non-verbal communication gestures exemplifying the employment of the six principles.