168 | 16 THE TESTERy
from approximately 282,000 tonnes of shipping lost per month during the early part of 1941,
to 64,000 tonnes per month by November. If Turing had not managed that, it is almost certain
that Britain would have been starved into defeat.
I had a glimpse of the Battle of the Atlantic when I met a friend of a neighbour not long ago.
He had been in the SAS during the war, a tough unit, and he made a crossing of the Atlantic
early in 1941. As he told me about it, his face darkened:
The worst days of my life. We left port with 21 ships and arrived in Britain with only 11. The
U-boats had downed 10 ships and left the survivors struggling in the water.
I used to see Turing from time to time. I have a strong mental image of him walking along
the corridor in one of Bletchley Park’s huts. With his gaze turned downwards, he was a shy
and diffident man, flicking the wall with his fingers as he walked, dressed in a mid-dark brown
sports jacket and baggy grey trousers. This is not your Achilles figure; he was not a warrior
king. But at that juncture, he was the most influential man in Europe bar none, and we owe our
freedom to him.
what was Tunny?
Tunny (or ‘Fish’, or as the Germans called it, the Lorenz SZ40) was a new, specially designed
machine, ordered by Hitler and used to encipher top-level messages between the German
Army headquarters in Berlin and the top generals, field marshals, and commanders-in-chief of
the huge forces on all the battlefronts (see Chapter 14). Tunny began with one link but spread
rapidly throughout Europe, since the German Army top brass valued it highly.
In 1940 Hitler’s mind was turning to his plans to dominate the whole of Europe. He knew
that there was going to be extensive fighting on land and that his generals were going to be
pretty busy. Up to this point, the German Army, Navy, and Air Force had used Enigma for
enciphering their messages, but Hitler was not satisfied with that: communications between his
generals and his headquarters needed something more powerful, more secure. So the Lorenz
company, a German electrical outfit, gave him a superb machine—Tunny. With twelve wheels
it was very advanced, highly complex, faster, and much more secure than the three- or four-
wheeled Enigma.
If you or I had to encipher a message we would probably use simple letter substitution, and
that would give us one level or layer of encryption. Tunny had not one, not two, but three levels
of encryption. Even two was a cryptologist’s nightmare: three was out of this world!
why was Tunny so important?
Tunny carried only the highest grade of intelligence. Top people signed the messages and
we used to see their names cropping up time and again in the messages that we broke: Keitel
(head of the whole German Army), von Jodl (Chief-of-Staff of the Army, the CEO), Rommel
(Commander-in-Chief, Normandy), von Runstedt (the Western Front), Kesselring (Italy), von
Manstein (the Russian Front)—and, of course, even messages signed by Adolf Hitler himself.
That’s not a bad start!