ASSUMPTIONS. 4. There is general expert agreement here and in America that bombs can be more easily and quickly made of plutonium than of uranium 235. Nevertheless it is a basic maxim of Scientific Intelligence that an enemy cannot be relied upon to follow the advice of our own experts however good that advice may be. It should, therefore, be pointed out that in circumstances other than those appertaining at present to the U.S.A. and Great Britain and with less knowledge than is available in those two countries, the U.235 separation procedure may seem preferable.