Secret Life of Bletchley Park - McKay Sinclair [37]
Herivel went on to calculate how such an error might be detected – and how the subsequent messages could be decoded. ‘I don’t think that I slept much that night,’ he now says lightly. It is not an exaggeration to say that it was one of the most startling breakthroughs made at Bletchley Park. Gordon Welchman was quick to assure young Herivel that he ‘would not be forgotten’.
The working-through of his insight was mathematical brilliance, but the original vision, that of the operator himself, was a flash of psychological genius – an understanding of human nature, rather than calculus. And this intuitive approach seems to be a recurring theme in the story of Bletchley Park, as had been seen with Dilly Knox’s use of ‘cillis’, or ‘Dilly’s Sillies’ as they were sometimes known. As Gordon Welchman wrote: ‘Unbelievable! Yet it actually happened, and it went on happening until the bombes came, many months later. Indeed … it seems to me that we must have been entirely dependent on Herivel tips and Cillis from the invasion of France to the end of the Battle of Britain …’2
One other non-scientific element helped the codebreakers, and that was the occasional foul language used by the German operators as they sent out multi-letter test messages. ‘The German operators with their German words were just oiks being oiks. Ask a chap to think of a word with four letters …’ says Keith Batey.
His wife Mavis points out the chilling converse of this. ‘Enigma would never have been broken but for those procedural errors. If, on the other hand, the German operators had all done exactly what they were told to do …’
But now the theoretical work at Bletchley Park was about to face the test of real firepower. Early in 1940, both the Allies and Germany had their own designs upon Scandinavia; the Allies realised that Hitler would want to grab bases in Norway in order to protect the safe sea-passage of iron-ore supplies from Sweden. Prime Minister Chamberlain was determined that British forces should land on the coast of Norway and take control of the iron-ore mines themselves.
However, while the Bletchley operatives were still trying to find ways of speeding up the decoding of Enigma, it appeared that the Germans had managed to penetrate the British code system. Informed of the secret British plans for Norway, Hitler urgently ordered the invasion of both Norway and Denmark. Though both countries had previously declared themselves neutral, this meant very little either to Hitler or to the Allies who had planned to come to their defence. For many in British High Command were convinced that a German attack on Britain was not far away.
Hitler’s invasion of Norway ironically gave the codebreakers another boost. It was at this time – when the number of intercepted messages had leapt upwards – that they broke the Yellow key, that used for the German campaign in Norway. The breakthrough provided a satisfying amount of intelligence about German movements, even if the Yellow key itself was only used for the duration of the Norwegian campaign. Much was learned about organisation and supplies. It was intelligence that had no immediate practical use, but the mere fact that such intelligence could be obtained was vital in itself. Moreover, the speed at which the messages were being decrypted was far greater than had previously been the case. Some could be cracked within an hour of being received by a transmission station.
There was, however, one immediate setback: no one at Bletchley Park or in the government departments knew exactly what to do with all this information. No one, it seems, was ‘equipped to handle the decrypts efficiently’. That meant that no one knew in what form to transmit the information to British commanders in