imposing checks at road blocks. These precautions, when enforced, would cause some re-evacuation of the population and would warn those who remained of impending danger. It would, however, take about 96 hours to evacuate the remaining 40% and it was most unlikely that we should get more than a few hours' notice of impending invasion. In view of this SIR ALAN BROOKE stressed the importance of enforcing the "stay put" policy, unless or until final evacuation was ordered. Our experience in France and Belgium had shown the danger of allowing the tide of evacuation to start, only to find it stemmed or turned by the arrival in rear of air-borne troops, by the activities of armoured formations or by the interruption of road communications by bombing.