There has been an explosion of interest in head worn displays in recent years, particularly for consumer applications with an attendant ramping up of investment into key enabling technologies to provide what is essence a mobile computer display. However, head mounted system have been around for over 40 years and today’s consumer products are building on a legacy of knowledge and technology created by companies such as BAE Systems who have been designing and fielding helmet mounted displays (HMD) for a wide range of specialist applications. Although the dominant application area has been military aviation, solutions have been fielded for solider, ground vehicle, simulation, medical, racing car and even subsea navigation applications. What sets these HMDs apart is that they provide the user with accurate conformal information embedded in the users real world view where the information presented is intuitive and easy to use because it overlays the real world and enables them to stay head up, eyes out, - improving their effectiveness, reducing workload and improving safety. Such systems are an enabling technology in the provision of enhanced Situation Awareness (SA) and reducing user workload in high intensity situations. These capabilities are finding much wider application in new types of compact man mounted audio/visual products enabled by the emergence of new families of micro displays, novel optical concepts and ultra-compact low power processing solutions. This paper therefore provides a personal summary of BAE Systems 40 year’s journey in developing and fielding Head Mounted systems, their applications.