 Starting in the summer of 1942 the TRE development team began experimenting with systems to project the display onto the windscreen, and by October had combined this with an image of the existing GGS Mk. II gyro gunsight to produce a true head-up display known as the Automatic Pilot's Indicator, or API. A single example was fitted to a Beaufighter and tested through October, and numerous modifications and follow-on examples were trialled over the next year.
