It seems Ferranti promised to demonstrate a computer at the Festival of Britain in 1950, but were unable to. So they built an electronic NIM-playing machine and called it NIMROD. “It’s absolutely terrifying” according to a commentator of the day. The machine was subsequently moved to and displayed at the Berlin Industrial Fair (a great story in itself).
Via the interesting blog post
The Priesthood at Play: Computer Games in the 1950s