The EM-1 was one of the British post-WWII rifle development projects with the ambitious goal of replacing both the infantry rifle and the submachine gun with a single select-fire weapon optimized for combat within 600 meters (as opposed to the prior doctrine of 1000m effective ranges). The design team was led by a man named Stanley Thorpe, and the first rifle was ready for test firing in December 1949.

Mechanically, the Thorpe EM1 used the same roller-locked operating system as the German Gerat 06 (note that it was locked, not roller-delayed). This would coupled with a long recoil gas pistol (the Gerat 06 had used a short stroke piston) and put into a bullpup configuration, chambered for the .280 British cartridge. Interestingly, it was also fitted with a mechanism which automatically dropped the bolt and chamebred a round upon the insertion of a loaded magazine. The basic operating mechanism has plenty of promise, but the implementation in this case was far too complex to have survived serious trials.

As NATO trials rapidly approached in the early 1950s, it became clear that the UK could not submit both The Thorpe EM-1 and the Janson EM-2 for testing. The EM-2 was a simpler rifle and more likely to succeed, and so the EM-1 was dropped from development and all efforts concentrated on the EM-2.