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New Scieotlst 23 February 1978 493
Pulling the crooked leg
Published next week are the memoirs of the wartime head of Air Ministry Scientific Intelligence.
Here he reveals some of the operations of the "most secret" war successfully waged in the backrooms
of Whitehall and In scientific laboratories all over Britain against the Germans*
PrMessor R. V.
Jones FRS
is pr-olessor of natural
philosophy al the
Universit..v of
Aberdeen. At the
outbreak of war he
was researching
infrared spectroscopy
at the Cla:rend.011.
Laboratory, Oxfprd
I was always aware that,. exciting
though Intelligence wast and im•
portant though its results mani
festly were, it was on a lower
plane of difficulty than research in
pure science.. Intelligence is a
parasitic activity; in that you are
always trying to discover what some other man has already done.
in contrast to entering an un
charted field yourseH. One of the
greatest difficulties in scientific research is to build up
your observational -experience in this new field, and to
develop concepts that have never entered any huanan
mind before. They may even appear to contradict long
established principles, as when Einstein proposed the
equivalence of mass and energy, ,or when de Broglie
postulated that material particles could also behave as.
waves" or when Bohr bad to conclude that the radial
acceleration of electrons in his orbits did not make them
radiate. Sometimes in lntellig,en-ce we experienced this
kind of difficulty, when for example it was necessary for
us to postulate that radio waves bent further round the
Earth than our own expert$ thought, or that rockets could
be made with a range greater than 100 miles; but all the
time I knew that we were trying to discover something
that bad already been discovered and formulated in the
minds of our Cerman opponents, and that it therefore
should be within our mental gr.asp.
To that ext~nt I felt that we were parasitic, and tackling
a basically easier job than that of research in pure science.
Even so, we sometimes had difficulties comparable with
those of scientific innovators when we bad to persuade our
experts to abandon some of their bithert.o accepted con
cepts. Moreover, the methods we used in gathering and
collating information wen? much the same in principle as
those employed in pure science. Where we oould claim to
be genuinely •creative was in de\'eloping new methods of
Intelligencet such as listening to radar transmissions, and
in welding them into a great system for observing the
enemy by as many means as possible"' and directing this
•MNc Seavt W«:.~ l. V. Ion• (WMl.11111 Ma"'8loft. '6•'5). ""' which th.-. uar,a. ha,,•
._. ak-. Is ,-,11111ithN on 'D felNwrr.
system and correlating the infor~ation that it obtained by
these means into a comprehensive reliable estimate of
enemy intentions.
We were remarkably fortunate in our opportunity. Just
as the impact of radio in the 1920s gave a unique chance
for every man to dabble in the "marvels of science" by
making his own receiver-a task complex enough to be
fasdnating without being so mm.plex, as television later
wa.s, that it was beyond the competence of the average
man-so it was with Scientific Intelligence in the Second
World WarI and for much the same reason. The very
development in science and technology that led to every
day radio in the 1920s also led to the radar and radio
navigational systems of the Second World War, and these
were relatively simple to understand and. if necessary,
frustrate.
Moreover, these developments in radio were of such
universal application in military technolog-y that they gave
me the entry to fields which at first sight might have
seemed quite remote. Radar provided the key to the
German night defences, and thus enabled me to attack
those defences more fruitfully than through any other
channeli an.d it also enabled me to attack the ftying bomb
in a positive manner by going for the German radar plots
in their Vl trials at Peenemiinde. J was therefore able to
redu.ce some of our major Intelligence problems to, the
field that by good fortune I knew best.
Possibly the opportunity of Enigma might be vi w d in
the same light, for it involved radio communication at a
stage of sophistication that was just within the limits of
human ingenuity to "break".
At the outbreak of war, September 1939, I was billeted
at Bletchley with Sir Kenneth and Lady Macdonald at
Winslow, along with Commander Edward Travist who hap
pened to be Deputy Head .of the Government Code and
Cip-her School, the cryptographic headquarters that was
officially part of MIG. The head of the school was Com
mander Alexander Denniston, whom Travis: was to suc
ceed in 1942,. but who bad laid the foundations. of our
brilliant ayptographic successes. In our long evenings
together Travis discussed with me his problems in CQ-pto
grapby, and in particular the problem of trying to "break"
the German Enigma machine.


New Sdentist 23 February 1978
TIii• EnJgma encoder
The Enigma machine was a very ingenious arrangemcn_t of
cogged wheels,. each one of which had a sequence of studs
on both sides. with each stud on .one side being connected by
a wire to a pin on the -0ther side--the exact arrangement
of the. connections being one of the secrets of the machine
and the pin making contact \vith one of the stud on lhe
next ,vheel The machine had a typewriter keyboardt and it
was worked rather like a cydometer: every time the n1achine
was opera~ to encode a letter. one wheel would be turned
by one space; after tbi ,vbeel bad moved by enough spaces
to turn it through -0ne revolution, it \YOuld click its neigh
bouring wheel by one spaoo. The. wheels were thus never in
the same position twice. The basic encoding was effected by
the passage of an electTic current through lhl? stu_ds so that
when a letter was to, be encoded. the appropriate key would
be pressed ou the keyboard, and the resultant _cod~d letter
would be determined by the appropriate conducting path
through the studs, the studs on one wheel maklnJ.? suitable
contact with the pins on the neighbouring wheel A further
touch of ingenuity was to add a reversing arrangement at the
edge of the third wbeel, a,ain with st11ds cross-connected so
as to send the current backwaTds th:Fough the wb.eets by yet
another path. Tbe returning current lit a smaH electric bulb
which illuminated a particular letter on a second keyboard.
and thus indieated the enciphered equivalent of the letter
whose ~Y had originally been pressed.
t
..l!I8e
1i--:_Ju1c;!z,
lI1•i'
Figure J A j
four"'Totor >
Enigma which I
the German ,;11
Nav1J med. It l
defied the best I'
etrartl of c
Bletchlet, PMk ~
untit JHS .t.!.
L - - - -- -- -- - - - - -- - - - - -- - -- - - - - - - - - - - - - - -- - - - - -- --- L
Sometimes, as with Knickebein, the German aircraft
navigational system, a single short decode provided the
clinching evidence. And because there was every Jikeli·
hood that the Germans felt that they were secure in
Enigma, even a single message was likely to provide an
anchor of truth on whlch any explanation of German
activity could be confidently based, or a teuchstone against
which previously formed theories of German intentions
could be tested. Care was of oourse necessary-although
any one decode was Jikely to be 100 pet cent reliable, it
might well contain much less than the wboJe truth-a fact
that must always be borne i.n mind regarding information
from any source, however reliable. But the confidence with
which Enigma decodes could be used in constructing or
testing theories of enemy intentions was outstanding among aJJ the sources available to us.
Battle of the beams
On the morning of 12 June, 1940, I visited Group Captain
Blandy, the head of the RAF "Y" Service, which inter
cepted German radio signals. He banded me a scrap of
paper saying, "Does this mean anything to you? It doesn't seem to mean much to anybody here." I read:
"XNICllEBEIN. KLEVE, IST AUF PUNKT 53 GRAD 24 MINUTEN MORD
UND ElN GRAD WEST ElNG:EBICHIE1 ."
The word "Knickebeinn (crooked leg ) I had ear1i r
noticed in a fragmentary entry on a paper salvaged in
March from a shot.down Heinke} aircraft. Information
from a German prisoner suggested it to be some sort of
beamed beacon. 0 Klev " could be the west German town
that we koe,v as Cleves. where Anne came from . If so the
translation would run : ''Cleves Knicltcbe_in is confirmed (or established} at position 53° 24 minutes north and 1• west."
The geographical position referred to was a point in
England, roughly on the Great North Road a mile or so
south of Relford. I immediately told BJandy that it meant
everything to me, and that it suggested lbat the Germans
liad a radio beam transmitter called Knickebein set up at
Cleves, on the nearest German soil to England. and that the
existence of the beam bad been confirmed one way or
another at this position over England. I quickly recognised
that it was a decoded message, because I knew that during
the preceding hYo months Bletchley had begun to be suc
cessful in decoding some of the Enigma messages. This
particular one had been sent by the Chief Signals OOicer
of Flieger Korps JV at 1455 hours on 5 June, and had been
decoded four days later.
I had to go to the Cabinet Office to see Professor Frederick Lindemann, in response to a question about
German radar, and told him that I bad just received the· Kniclcebein message, and that I was convinced that the
Germans had an intersecting beam system for bombing
England; and if they could make narrow beams for navi
gation they could also make narrmv beams fm- radar.
Lindemann immediately said that the beams would not
work for radionavigation, because they would have to use
short waves which would not bend round the curvature of
the Barth. Armed with some computations by T. L. Eckers
ley, I told him that, contrary to what he supposed, they
would.
The bombers available to Flieger Korps IV were
Beinkel ms of Kampf Geschwadern 4 and 27. Whatever
equipment was used for receiving the Knickebein beam
must be capable of being fitted to this type of aircraft.
Squadron Leader Denys Felkin, chief interrogator at
Bletchley, had prisoners from the bombers shot down dur·
ing the preceding few nights, so I briefed him about the
information that I needed.
He duly interrogated the prisoners without at first get
ting anything of value. But when the prisoners were alone
one of them said to another that no matter bo\v hard we
looked ,ve would never find the eq_uipment This could
not have been a better challenge because it implied that
the equipment was in faet under our nose$, but that we
would not recognise it. I therefore obtained a copy of the
full t chnicaJ examination of the Heinkel m that had been
shot do\vn in the Firth of Forth raid, and looked especially
at the various items of radio equipment. The only item
that could possibly fill the bill was the receiver that was
carried in the aircraft for the purpose of blind landing. It
¥.~as labelled as E.Bl.I (which stood for Empfanger Blind I
-blind landing receiver type l ) and was ostensibly for the
normal purpose of blind landing on the Lorenz beam
system, which was by then standard at many aerodromes.
N. Cox Walker at Farnborough, who had evaluated the
equipment, then told me that although there was .nothing


New Scientist 23 February 1978 495
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.. ,,,to,1"'""'~1:,,._-,c:,.. 1 - t-1-._ AtTtn,, tr.
O~N(. A~~ i>O'
FigUTe 2 (above) The L~rger', musczge and s1'etch.
fop right R. V. Janus sketch of the HagtLB .Kn.ickabein.
Bottom right Beinhel JU wUh cmten.noe for X-oeam guidance
unusual about the blind landing receiver, it was much
more sensitive than would ever be needed for blind land
ing. So that was it. I now knew the receiver, and the
frequencies to which it could be tuned, and therefore on
which the Knickebein beam must operate. And in a short
time we heard the beams for ourselves.
Although it was worth squeezing every drop 8f information out of the Enigma decodes, it would have been dan•
gerous to rely on them too much, and thus to neglect other
sot1roes. Io a sense, cryptography was the most vulnerable
sour,ce of all in that it collld have been extinguished at any
time by a few simple changes in the Enigma machine. At
the end of every investigation I therefore looked back to
see how far we could have gone without Enigma As the
outstanding example, it was reassuring to· find that we
would very probably bave raided the rocket-launching sites
at Peeoemiinde without any help from Enigma. This
observation is not intended in the slightest to belittle the
enorm.ous contribution made by those who brok~ the
Enigma traffic-quite the reverse. And it is a pleasure to
know that in a war in which scieor.e, and especially pbJsical
science, gained great esteem, the cootn'butions of our
colleagues in mathematics .and in some of the arts subjects
can at last be publidy recognised.
Det ■ ctin1 the •v• llodtet ...II
The message about a rocket that we received from a
Danish chemical engineer in December 1942 resensitised
us to a possibility which, although I had reported it in 1939,
had no more than stayed in the background of our
thoughts over the intervening hectic years with the beams
and German radar. A report received fr-om Oslo had men• tioned Peenemiillde. where, it had said, radi<><ontrolled
rocket gliders were being developed for use against ships under the code name .PZ21 (PerngestcwerteZielftnoeug).It
also said, although it did not mention Peenemunde in this
connection, that rocket shells 80 centimetres in diameter
were being developed for use against the Maginot Jjne;
thes-e were ~stabilised, but were prone to fty ju uncon
trollable curves. and so radio ooutrol was being considered.
~
II
• I I'III
The Danish engineer's warning was timely: when be
sent his message only thxee prototype v.2 rockets had iD
fact been fired at Peenemiinde, the first suocessful firing
being on 3 October, 1942. This was as good a warning as
we could hope to achieve in view of our lack of Scientific
lutelligen~ before the war, which had forced me to con•
ceutrate on detectiog the development of new weapons at
the trial stage, ie later than the research stage but. hope-
fully, before the operational.
Over the aext three months a few further reports
appeared, but noae substantially added to our knowledge.
Indeed, they could have been no more than rumours, and
the turning point, as far as I was coocerned, occurred on
Z'l March, 1943. My colleague Charles F~ank (now Sir
Charles Frank, PBS) was reading the transcripts of a con,.
venation between two German generals, who bad been captured after el Alamein, and who were now at our
Interrogation Centre. One was Cruewell, who had been
Rommel's Second-in-Command The other was von Thoma.
A remark of von 'Thoma to Cruewell on 22 March. 1943,
caught Frank's attention. Translated, this ran:
-bot no progress whatsoever can have been made in
this rocket business. I saw it once with Feldmarschall
Btauchitscb, there is a special gl'ound near Kunersdorf


498 New Sden1llt 2S February 1978
(?) . . . They•ve got these .huge things which they've
brought up here . . . They~ve always said they would go
15 kms. into the stratosphere and then . . . You only aim
at an area . . . If one was to . . . every few days . . .
frightful . . . The major there was full of hope-he said
'Wait until next year and the fun will start!' . .. There's
no limit (to the range).
Von Thoma also said that he knew their prison was some
where near London and since they had beard no large
explosions, there must have been a hold-up in the rocket
programme.
His remark transformed the situation. An Intelligence
organisation bears many resemblances to the human head,
with its various senses. These will generally be on the
alert, each searching its own domain and then as soon as
the ears, for example, bear a noise and the signals are
received in the brain, the latter will direct the eyes in the
appropriate direction to supplement the information from
the ears by what the eyes can see. So, if one kind of
Intelligence source produces an indication, the Intelligence
organisation should then direct other kinds of source to
focus on the same target.
It was ''Pop.. Stewart and his colleague Roddie Nicholson
from the Assistant Directorate of Intelligence (Photos) who
played an essential part in my finding the first rocket, f:or
they provided me with photographs of Peenemilnde.
Although aerial photographs had first to ,go to Duncan
Sandys, in contrast reports from secret agents had to c-0me
through me, so that a1though I only saw aerial photographs
some days after the Sandys •organisation, I saw the agents'
reports some hours earlier. There were two in particuJar
in JuM 1943 that remain in my memory. They came from
two Luxembourgers whom the Germans had conscripted
into the army of foreign construction workers. in Peene·
miinde. One was Leon Henri Roth. a student aged 20, who
bad been expelled from school for starting a Resistance
cell. Along with other Luxembourgers he was sent to
P-eenemilnde, and succeeded in getting letters through to
his father. who was a member of a Belgian nehYork, telling
of the development of a large rocket which made a noise
resembling that of "a squadron at low altitude". 'lbe
other Luxembourger whose report I remember was Dr
Schwagen, afterwards director of the Laboratoire Bacterio
logique de l'Etat in Luxembourg, who sen·t thl'ough an
organisation known as the nFamille Martin" a report and
sketch which reached me on 4 June. It is shown in Figure
2. and it clearly mentioned a rocket of about 10 metres
length, and showed where it was assembled. It also stated
that for firing it was mounted on a cubical structure. Dr
Schwagen survived the war but tragically Roth was killed
by fire from an American tank in 1945, wbile escaping with
two Frenchmen in a German military car.
For much of the war. I was concerned that 1 might have
an opposite number in Germany, quite possibly my pr~war
Oxford friend Car) Bosch, who might .have provided me
with false clues. as Bosch himself certainly could have
done. This would at minimum have made my task more
difficult, and could easily have misled me onto several
false trails. As it turned out, though, there was no such
cooperation between science and the Services in Germany,
and so we were spared this problem-and many others. It
was the great contribution of the generation of scientists
before mine, headed by Henry Tizard (f,ormerly Secretary
of the Department of Scientific and Industrial Research)
an~ Frederick Lindemann (professor of experimental
philosophy at Oxford). Accentuated by the emergency in
w.hicb Britain found itself after 1933, serving officers and
scientists worked together to an extent far exceeding that
of our opponents. Further, there was leadership. In Cburcbill we had a
Prime Minister with a genuine and strong interest in the
possibilities opened up by science, such as none of his
successors has had. Even his controversial dependence on
Lindemann was evidence of this interest which, for
example, made him anxious to be flown-even at some
disoomfort- in experimental aircraft to see foT biroself the
state of airborne radar.. After our first meeting I felt that
there was now so strong an appreciation at the top that in
emergency J could have appealed to him with confidence,
although I also felt that so long as Charles Portal was
Chief of Air Staff no appeal would ever be nec-essary. ._.Your
name". Churchill once said to me. "will open all doors!.,
Right through to the end of the ·war I was able to keep
my immediate Intel)igenc,e organisation small, and to use
the initiative of individuals to the full. Had we been a
little bigger, we should have had to institute an internal
communication system, instead of depending on personal
contacts to the extent that we did, and this would have
slowed our daily working. But there are many tasks in
Intelligence that require large numbers. of people, and
these tasks- have multiplied since 1945; there are, for
example, many more radar and guidance systems com
pared with those with which we had to deal, and they
require armies of recording operators and interpreters if
they are to be unravelled. Scientific Intelligence organisa
tions therefore now have to be larger, and the consequent
change of scale from that on which we operated may well
involve a different balance of qualities in those heading
the organisation.
Eni1matic fruits
Our work was exhilarating. Tragedy, such as the loss of
Tony Hill (our outstanding photographic pilot) or the men
of the first Rjukan raid on the heavy water plant, was
always near; and tension, as in tbe Blitz or the "V" cam
paigns, \Vas often acute; but there were moments of
tremendous excitement, as in the finding of the Knickebein
beams. And these moments continued throughout the war :
the first time \Ve knew an X-beam target in advance of the
raid; the photographs of the first Freya and Wurzburg
German. home and coastline defenc,e radar systems; the
Bruneval Raid on the F'reyas; the searchlight map; the
unravelling of the Kammhuber Lin.e in a flash ; Window
(the "smoke screen" on radar); the finding of the rockets
at P•eenemilnde and Blizna; the first V-1 tracks in the
Baltic; D-Day; the true weight of the V-2. 1 felt matched
to. the ta~ with an operational r-eward awaiting almost
everything that I did; and I worked with as brave a com
pany of men and w,omen as anyone might hope to meet.
Even such a simple operation as countering the beams
involved a multitude of men and women, every one of
whom played an essential part; patiently cataloguing the
call signs of German aircraft, poring over innumerable air
photographs only a fraction of which had anything interest·
ing on them. working away at breaking the seemingly
unbreakable Enigma machine, interrogating prisoners,
examining captured equipment, listening to the beams and
soouring tbe country to 6nd suitable jamming transmitters,
and setting these onto the right frequencies, all played
their part-and the whole system would fail when any one
part broke down. When to all this are added the contribu
tions by those who risked and sacrificed their lives, our
own efforts may perhap be seen in a more reali tic per
spective. We au depended on the efforts of a great body
of m n an·d women whose existence in Lord Slim's words,
''is only remembered wh n something for which they are
r~sponsible go s wrong''.
If any one of these n_1any components had failed, our
entire effort would have come to nothing. Just as any one
link in a chain is e ential to upporting the weight at its
end, or as a breakdown in any one component can ruin a
machine, so could any one of many agencies have lost us
the war. What none of them would have claimed is that it
,von the war by itself. 0