At the end of tape from Radiohead’s OK Computer OKNOTOK 1997-2017 bonus material there is a ZX Spectrum program. Also, inside the code there’s a hidden, black text on a black background: “congratulations….you’ve found the secret message syd lives hmmmm. We should get out more”. If you would like to repeat this yourself here is a guide how to do this written by Maciej Korsan here.