listening-posts and
teleprintered to Bletchley and within ten minutes of transmission,
even as the U-boats were preparing to dive, they were emerging via
a tunnel into Hut 8’s Registration Room. Jericho helped himself to
the contents of a wire basket labelled “Shark” and carried them to
the nearest light. The hours immediately after midnight were
usually the busiest time. Sure enough, six messages had been
intercepted in the last eighteen minutes. Three consisted of just
eight letters: he guessed they were weather reports. Even the
longest of the other cryptograms was no more than a couple of dozen
four-letter groups:
JRLO GOPL DNRZ LOBT—
Puck made a weary face at him, as if to say: What can you
do?
Jericho said: “What’s the volume?”
♦
“It varies. One hundred and fifty, perhaps two hundred messages
a day. And rising.”
The Registration Room didn’t just handle Shark. There was
Porpoise and Dolphin and all the other different Enigma keys to log
and then pass across the corridor to the Crib Room. Here, the
cribsters sifted them for clues—radio station call signs they
recognised (Kiel was JDU, for example, Wilhelmshaven KYU), messages
whose contents they could guess at, or cryptograms that had already
been enciphered in one key and then retransmitted in another (they
marked these “XX” and called them “kisses”). Atwood was the
champion cribster and the Wrens said cattily behind his back that
these were the only kisses he had ever had.
It was in the big room next door—which they called, with their
solemn humour, the Big Room—that the cryptanalysts used the cribs
to construct possible solutions that could be tested on the bombes.
Jericho took in the rickety tables, the hard chairs, the weak
lighting, the fug of tobacco, the college-library atmosphere, the
night chill (most of the cryptanalysts were wearing coats and
mittens) and he wondered why—why?—he had been so ready to come
back. Kingcome and Proudfoot were there, and Upjohn and Pinker and
de Brooke, and maybe half a dozen newcomers whose faces he didn’t
recognise, including one young man sitting bold as you please in
the seat which had once been reserved for Jericho. The tables were
stacked with cryptograms, like ballot papers at an election
count.
Puck was muttering something about back-breaks but Jericho,
fascinated by the sight of someone else in his place, lost track
and had to interrupt him. “I’m sorry, Puck. What was that?”
“I was saying that from twenty minutes ago we are up to date.
Shark is now fully read to the point of the code change. So that
there is nothing left to us. Except history.” He gave a weak smile
and patted Jericho’s shoulder. “Come. I’ll show you.”
When a cryptanalyst believed he’d glimpsed a possible break into
a message, his guess was sent out of the hut to be tested on a
bombe. And if he’d been skilful enough, or lucky enough, then in an
hour, or a day, the bombe would churn through a million
permutations and reveal how the Enigma machine had been set up.
That information was relayed back from the bombe bays to the
Decoding Room.
Because of its noise, the Decoding Room was tucked away at the
far end of the hut. Personally, Jericho liked the clatter. It was
the sound of success. His worst memories were of the nights when
the building was silent. A dozen British Type-X enciphering
machines had been modified to mimic the actions of the German
Enigma. They were big, cumbersome devices—typewriters with rotors,
a plugboard and a cylinder—at which sat young and well-groomed
debutantes.
Baxter, who was the hut’s resident Marxist, had a theory that
Bletchley’s workforce (which was mainly female) was arranged in
what he called “a paradigm of the English class system”. The
wireless interceptors, shivering in their coastal radio stations,
were generally working-class and laboured in ignorance of the
Enigma secret. The bombe operators, who worked in the grounds of
some nearby
teleprintered to Bletchley and within ten minutes of transmission,
even as the U-boats were preparing to dive, they were emerging via
a tunnel into Hut 8’s Registration Room. Jericho helped himself to
the contents of a wire basket labelled “Shark” and carried them to
the nearest light. The hours immediately after midnight were
usually the busiest time. Sure enough, six messages had been
intercepted in the last eighteen minutes. Three consisted of just
eight letters: he guessed they were weather reports. Even the
longest of the other cryptograms was no more than a couple of dozen
four-letter groups:
JRLO GOPL DNRZ LOBT—
Puck made a weary face at him, as if to say: What can you
do?
Jericho said: “What’s the volume?”
♦
“It varies. One hundred and fifty, perhaps two hundred messages
a day. And rising.”
The Registration Room didn’t just handle Shark. There was
Porpoise and Dolphin and all the other different Enigma keys to log
and then pass across the corridor to the Crib Room. Here, the
cribsters sifted them for clues—radio station call signs they
recognised (Kiel was JDU, for example, Wilhelmshaven KYU), messages
whose contents they could guess at, or cryptograms that had already
been enciphered in one key and then retransmitted in another (they
marked these “XX” and called them “kisses”). Atwood was the
champion cribster and the Wrens said cattily behind his back that
these were the only kisses he had ever had.
It was in the big room next door—which they called, with their
solemn humour, the Big Room—that the cryptanalysts used the cribs
to construct possible solutions that could be tested on the bombes.
Jericho took in the rickety tables, the hard chairs, the weak
lighting, the fug of tobacco, the college-library atmosphere, the
night chill (most of the cryptanalysts were wearing coats and
mittens) and he wondered why—why?—he had been so ready to come
back. Kingcome and Proudfoot were there, and Upjohn and Pinker and
de Brooke, and maybe half a dozen newcomers whose faces he didn’t
recognise, including one young man sitting bold as you please in
the seat which had once been reserved for Jericho. The tables were
stacked with cryptograms, like ballot papers at an election
count.
Puck was muttering something about back-breaks but Jericho,
fascinated by the sight of someone else in his place, lost track
and had to interrupt him. “I’m sorry, Puck. What was that?”
“I was saying that from twenty minutes ago we are up to date.
Shark is now fully read to the point of the code change. So that
there is nothing left to us. Except history.” He gave a weak smile
and patted Jericho’s shoulder. “Come. I’ll show you.”
When a cryptanalyst believed he’d glimpsed a possible break into
a message, his guess was sent out of the hut to be tested on a
bombe. And if he’d been skilful enough, or lucky enough, then in an
hour, or a day, the bombe would churn through a million
permutations and reveal how the Enigma machine had been set up.
That information was relayed back from the bombe bays to the
Decoding Room.
Because of its noise, the Decoding Room was tucked away at the
far end of the hut. Personally, Jericho liked the clatter. It was
the sound of success. His worst memories were of the nights when
the building was silent. A dozen British Type-X enciphering
machines had been modified to mimic the actions of the German
Enigma. They were big, cumbersome devices—typewriters with rotors,
a plugboard and a cylinder—at which sat young and well-groomed
debutantes.
Baxter, who was the hut’s resident Marxist, had a theory that
Bletchley’s workforce (which was mainly female) was arranged in
what he called “a paradigm of the English class system”. The
wireless interceptors, shivering in their coastal radio stations,
were generally working-class and laboured in ignorance of the
Enigma secret. The bombe operators, who worked in the grounds of
some nearby
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