Code-breaker test | Blue Peter
Blue Peter continues the mission to find CBBC Intelligence Officers. Over 5000 viewers applied but only three get the chance to go inside MI5's Headquarters.Tweet
Project Enigma - Cracking codes in London | Blue Peter
The competition winners use a replica working Enigma machine to crack their own puzzle set by GCHQ.
Project Enigma - GCHQ Tour and challenge | Blue Peter
The competition winners, get their first look inside GCHQ and are given their top-secret mission to crack.