The traffic exchanged between Moscow and London during the period February 1934 to January 1937 was transmitted in cipher, and the fact that the parties involved used such surreptitious means for their communications, instead of the ordinary, commercial cables, indicates that the messages were never intended to be read by anyone else, and therefore is something of a guarantee that the content would be of interest to MI5. According to William Morrison, the wireless operator who underwent a lengthy debriefing by Max Knight and John Archer, even he was not allowed to encipher the clear text, and he only handled ciphered messages.