to be unnecessary, a temporary platform devised by the Royal Electrical and Mechanical Engineers and made from railway sleepers and rails was found to be adequate for the static guns, making them considerably easier to re-deploy as the V-1 threat changed. The development of the proximity fuze and of centimetric, 3 gigahertz frequency gun-laying radars based on the cavity magnetron helped to counter the V-1's high speed and small size. In 1944, Bell Labs started delivery of an anti-aircraft predictor fire-control system based on an analogue computer, just in time for the Allied invasion of Europe. These electronic aids arrived in quantity from June 1944, just as the guns reached their firing positions on the coast. Seventeen percent of all flying bombs entering the coastal "gun belt" were destroyed by guns in their first week on the coast. This rose to 60 percent by 23 August and 74 percent in the last week of the month, when on one day 82 percent were shot down. The rate improved from thousands of shells for every one V-1 destroyed to one for every 100. This mostly ended the V-1 threat. As General Frederick Pile put it in an April 5, 1946 article in the London Times: "It was the proximity fuse which made possible the 100 percent successes that A.A. Command was obtaining regularly in the early months of last year...American scientists...gave us the final answer to the flying bomb." Barrage balloons Eventually about 2,000 barrage balloons were deployed, in the hope that V-1s would be destroyed when they struck the balloons' tethering cables. The leading edges of the V-1's wings were fitted with Kuto cable cutters, and fewer than 300 V-1s are known to have been brought down by barrage balloons. Interceptors The Defence Committee expressed some doubt as to the ability of the Royal Observer Corps to adequately deal with the new threat, but the ROC's Commandant Air Commodore Finlay Crerar assured the committee that the ROC could again rise to the occasion and prove its alertness and flexibility. He oversaw plans for handling the new threat, codenamed by the RAF and ROC as "Operation Totter". Observers at the coast post of Dymchurch identified the very first of these weapons and within seconds of their report the anti-aircraft defences were in action. This new weapon gave the ROC much additional work both at posts and operations rooms. Eventually RAF controllers