Our intention to regard the closing of the Straits as a casus belli was communicated...to the foreign ministers of those states which had supported international navigation in the Straits in 1957 and thereafter. There can be no doubt that these warnings reached Cairo. One thing was now clear. If Nasser imposed a blockade, the explosion would ensue not from 'miscalculation', but from an open-eyed and conscious readiness for war.