(Due to arrive Canberra 13.4.29)

My dear P.M.,

An incident has occurred in connection with a paper on Coast
Defence on which I have written a long letter to Henderson [1],
the contents of which I have asked him to take an early
opportunity of discussing with you. I have written it to him
rather than direct to you for two reasons-firstly he can choose an
appropriate moment to discuss it with you when you are rather less
pressed than usual-and secondly it is well for him to be
thoroughly impressed with the combination of tact and secrecy with
which certain documents have to be treated. I will not burden you
with the story here, other than to say that although the incident
in itself is not of major importance, it is typical of possible
incidents which might have much more serious consequences. I do
not think it would be wise to make a real disturbance about this
incident, but I think it would be appropriate to have a word with
the Defence Minister [2] and General Chauvel [3] about it-although
this of course is for you to decide.

It is unfortunate that this incident should have happened with
regard to Belligerent Rights as this is a subject on which the War
Office are particularly touchy. As it has been put to me by an
officer in intimate touch with all the services, the War Office
are fighting with their backs to the wall as they are very much
afraid that they may lose a good deal of their grip on Coast
Defence. Since the War, the War Office have lost the defence of
Iraq and Aden, they are being pressed very hard by the Air
Ministry with regard to the Defence of the Sudan and, to a lesser
extent, with regard to the North-West Frontier of India. All this
has meant an increase of prestige for the Air Ministry at the
expense of the War Office-and the latter are naturally going to
fight to the last ditch to maintain their previous position in
respect of Coast Defence. This means, in short, that they will
press their claim to defend ports by guns rather than let the Air
have any finger in the pie by supplanting guns by torpedo carrying
and other aircraft.

This is the reason why the War Office do not want any of their
adumbrations to be known to anyone but themselves in case they
should be used against them in the final struggle which will be
staged at the C.I.D.

The danger of this incident is that it may make the War Office
take the attitude in the C.I.D. that no Defence documents on War
Office subjects (either C.I.D. or otherwise) should go to any
Dominion other than through the Dominions Office or for the
quarterly circular letter from the C.I.G.S. If they were to raise
this matter officially at the C.I.D., it might result in a
considerable curtailment of this valuable source of information on
Defence matters.

However, my conscience is clear in the matter of this incident and
Hankey [4] is quite satisfied and has appeased the War Office by a
letter of explanation. But I think a word from you at the
Australian end is rather called for.

I am, Yours sincerely,
R.G. CASEY