The game they said couldn't be done... And that was Team17 themselves. When Andy Clitheroe walked onto the Team17 Stand at the September 1994 ECTS with a demo of this game engine, he was signed up immediately.
Team17 contacted John Carmack at ID Sftware, to see if they could acquire the Doom licence to use with this engine. ID refused, sort of. In fact they set the price for the licence so high that the game would have been uneconomic to produce. So Team17 dusted down their trusty Alien Breed series, and made a fine 3D first person shoot em up regardless.
AB3D had some tricks up its sleeve that even Doom couldn't match, and fans say it was the most atmosphere-laden first person game available on any platform at the time.