Lesson observation has been widely debated in education circles in recent times. From politicians to practitioners, everyone seems to have a view on it. Surprisingly, however, very little empirical research has been done on this important area of practice. With this in mind, this article explores some of the findings from a national research project investigating the use and impact of lesson observation on the professional lives of thousands of staff working in the further education (FE) sector. The project, sponsored by the University and College Union (UCU), adopted a mixed-methods approach and was carried out over a year (2012-13). This article argues that lesson observation has become a central crucible in which power is exercised over individuals and institutions alike under the guise of measuring and improving teacher performance. It considers what lessons can be learnt about its current use and concludes with recommendations as to what needs to change to enable the education sector to make better use of observation in the future.