This notice records the Bletchley Park’s staff’s feelings at first decoding an enigma message:-

This is a replica bombe, the proto computer used to find ‘matches’ for Enigma encoded messages, leading to their decoding.

Every five minutes or so the replica simulates the operation of the originals. It’s very noisy. One of the huts elsewhere on the site housed several of these machines. Imagine the din!:-

Colossus was the first electronic computer; used at Bletchley Park to help decode enemy messages:-