There's some rather amusing, and I suppose a nod to 'horizon scanning' when in this day and age we're so occupied with possible defence cooperation (both industry and strategy) when in 1963-4 the Japanese approached us for such terms and the Admiralty/War Office blocked it. 1/

A couple of examples include the Tigercat/Seacat sale to the Japanese being blocked successfully for a year by the MoD and an invitation to the Malaysian jungle warfare school being rescinded. 2/

Most of the reasoning was based on 'security grounds' (which is a bit nebulous if you ask me).

The British Embassy in Tokyo offered some more concrete concerns (though the Foreign Office was broadly in favour). Citing fear of American influence. 3/