An extract from Air Scientific Intelligence Interim Report on German Long-range Rockets, 26 June 1943 (DEFE 40/12)
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The evidence of the existence of a long range rocket is reviewed; this evidence comes mainly from three types of source: secret agents, prisoners-of-war, and photography. Collateral evidence from other types of source is considered.
The evidence shows, beyond doubt of "planting", that the Germans have for some time been developing a long range rocket at Peenemunde. In its present form this rocket is about 38 feet long by 6-7 feet diameter, with probably three tail fins, and a weight of 40-80 tons; it has been photographed. It is uncertain how much of the development and constructional work is done at Peenemunde, but it would be consistent with the large majority of the reports if Peenemunde were the sole site.
The principal trouble experienced has been that of controlling the rocket in flight, and it is doubtful whether this trouble has yet been entirely overcome. The technical authorities would therefore probably prefer to delay using the rocket until next year at least, but the Fuhrer is said to be demanding its operation as soon as conceivably possible, within the next few months. In this case the rocket is likely to be erratic, and London would be the only worthwhile target. The present production of rockets is probably small, so that the rate of bombardment would not be high. The only immediate counter measure readily apparent is to bomb the establishment at Peenemunde.