Initially Lorenz messages were manually deciphered by linguists and others in the Testery.
To demonstrate this in 2014, Captain Jerry Roberts (a Testery code-breaker), at the age of 93, recreated two Tunny (Lorenz) messages in "depth". A depth was when two messages were sent using the same wheel settings. This gave the code-breakers a potential opening to decipher the message by hand and was how Colonel Tiltman made the first break. Breaking Lorenz codes by hand was a very time-consuming process.