By Milo Boyd Drivers could find themselves having their insurance invalidated if they are making a little known about but easy to commit mistake. According to the RAC, an estimated 2.9million people across the country are thought to use a dashcam in their vehicle. They are used by many drivers to protect them from fraudulent claims or to film the illegal driving behaviour of others. Many dashcam users are also benefiting from cheaper insurance since some providers offer lower premiums for motorists that have the recorded devices fitted. As convenient as that may seem for your purse strings, da…