My dear P.M.,
Defence of Ports: I remember that in conversation with you before I left Canberra, the fact that you had done nothing to implement the Australian Coast Defence Report (C.I.D.)  seemed to be rather on your consciencethis combined with your known desire for economy induced me yesterday to send you a telegram in this regard, which was inspired by my knowledge that New Zealand were doing nothing about their Coast Defences on the plea of possible air developments, that H.M.G. were doing nothing about home and colonial port defence on the plea of economy, and that the South African Coast Defence Report (now in process of gestation) raised some doubt as to the wisdom of going ahead with the conservative and standardised advice that the C.I.D. had given us.
The question as to where the truth lies as between the contentions of the Air Ministry on the one hand and the Admiralty and War Office on the other, regarding the defence of ports, has created a good deal of dissension at Chiefs of Staff Committee Meetings and C.I.D. Meetings in recent years.
It has arisen, to my immediate recollection, in the cases of the defence of (1) Singapore Base, (2) Aden and (3) South African Ports.
It creates considerable feeling at all meetings at which it is discussed and it has been the rock on which the Air Ministry and Admiralty have split on many occasions.
It is essentially a question as between the Admiralty and the Air Ministry -with the War Office usually taking the side of the Admiralty.
The ex parte stand taken by each Chief of Staff is quite noticeable. When it comes to a question on which their particular service stands to lose or gain prestige, it seems to me that they cease to think of themselves as joint members of the Chiefs of Staff's Committee-and revert to being members of their particular services energetically exercised in defending their young.
It has always been a question that interested me and soon after I returned, and without any knowledge that the Air-Navy question had been ventilated while I was away from London, I plunged into it again with several friends here belonging to the services. My object was to discover whether it was worth while suggesting to you (as being outside the fray) to ask H.M.G. officially for an expression of considered opinion on certain essential and hitherto undecided points connected with the 'Air versus Ships' and 'Air versus fixed land defences' controversies.
I soon discovered that the problem had arisen in the last year in the case of the defence of Aden and the defence of the South African ports. I write of these two matters in other letters by this mail.
I regret that I cannot send you the South African Report by this mail, but I have been asked not to do so-and rightly so-as it consists to date of the three memoranda of the individual Chiefs of Staff-they not having been able to agree on the matter. I am told that it is probable that the three individual Chiefs of Staff's reports will be sent on to South Africa with a covering note saying 'Herewith, for what they are worth', and going on to say that as South Africa is fairly immune from possible attack through distance and as the Foreign Office assure us that war is at least ten years off-that H.M.G.'s confidential advice is to await developments and not in the meantime to spend much money.
There is enough parallel between South Africa's position and our own to warrant some hesitation on our part before we spend much money on the rejuvenating of our coast defences on standard lines.
However, as I imagine you will want something official to go on, I suggest that you might cable H.M.G. and say that in view of the apparent reluctance all round to spare money on fixed coast defences and that as the Commonwealth is endeavouring to avoid all expenditure that is not immediately necessary, what then is the advice of the C.I.D. as to your going on with the programme they advised. 
Hankey  says that in the event of your sending a telegram of this nature, it is almost certain that the reply of the C.I.D.
would be that they do not consider that the programme is urgent.
I am, Yours sincerely, R. G. CASEY