Dear Mr. Bruce,
Both the Foreign Office and the Colonial Office have raised the point that they do not wish secret information to go by cable to you in any other cypher than one approved by themselves. They do not approve the cypher 'B', the one in use by Australia and of which I have a copy, as they say that the mere length of time that it has been in use renders it of little value.
I then said that I was in their hands with regard to a cypher and they have come to the conclusion that I should be supplied with a copy of one of the secret cyphers used by the Governor-General.
 They will be cabling you in a few days' time asking you to receive from the Governor-General copy of a certain cypher for use in cable communication with me.
The above will be for use only for information of the most confidential character. For everything else I can use either cypher 'B' or the ordinary Government Code.
With regard to the secret cypher that your Office will receive from the Governor-General I am asked to say that they wish it to be kept in the hands of Dr. Henderson  or someone of similar rank.
I am, Yours sincerely, R. G. CASEY