4. We cannot say that the withdrawal of all anti-aircraft and searchlight defences from the London area if known to the Germans, would have no influence whatever on a decision by them whether or not to attempt a raid. We still believe, however, that the major deterrents to an attempt are the factors set out above. Nor can we say that the absence of all such anti-aircraft and searchlight defences would have no bearing on the effectiveness of a raid, if attempted. We believe, however, that interference by fighters and radar would be the major factor bearing on the effectiveness of any attempted raid.