The RADAR lock has been around for almost 30 years. By modern standards, it is not very sophisticated and this is both an advantage and a source of criticism. The lock is designed for access and privacy. When fitted correctly, the outside indicator turns red to show that the loo is occupied. When the user pushes the handle on the inside upwards, entry is impossible for anyone else, even if they have a key. Where access is needed, for example in a medical emergency, and the door is locked in this way, a flat headed screwdriver or a penny coin can be inserted into the outside plate and turned to open the lock. This provides a good balance between privacy and safety, in the rare event that someone should need help, for example as a result of a fall or a seizure. If the lock is fitted incorrectly then, yes, the door can be opened by another keyholder, as the lock is not engaged. This could have happened because a right hand set has been fitted to a left hand door or vice versa....