by Helen Fry
On 28 December 1939, Trench met with Alastair Denniston, the first head of the Government Code and Cypher School (GC&CS) at Bletchley Park. Denniston, who had a background in naval intelligence and codes from the First World War, was concerned about breaking the German naval Enigma code in the new war. Trench noted in his diary: ‘Colonel Denniston came in to tell me about his camp.’43 It is possible to infer from this entry that, prior to this, Trench had no knowledge of Bletchley Park.
Two days later, on Saturday 30 December, naval interrogator Pennell was sent to Bletchley to discuss ways of securing Enigma intelligence from Erich May who was being held at Trent Park.44 Prisoners had been talking amongst themselves about German codes, decoding methods and cyphers (all picked up by the hidden microphones), but the interrogators at Trent Park needed to understand exactly what intelligence was required by the code-breakers.
The entry in Trench’s diary is an indication of the early intelligence cooperation between Trent Park and Bletchley, and of a relationship that would continue throughout the war.45 Both sites were highly top secret and not all personnel at Kendrick’s site were cleared for knowledge of Ultra – the wartime signal intelligence obtained at Bletchley Park from cracking the high-level encrypted messages of the enemy.46
On New Year’s Day 1940, Pennell went out to Trent Park to see Erich May and tried the softer approach.47 May had already been taken for trips into central London and had confided to another prisoner:
He [Lt Pennell] invited me alone to his house where he is living for the time-being only with his butler. His wife is on the west coast. He has a number of country estates, one in the West of England, and another in South Africa and his fine house in London. We had a very good meal and drank only champagne and port. He is a fine fellow. I believe him when he says he only has a personal interest in me.48
May’s preferential treatment was designed to soften him up. During the interrogations, which were more like friendly discussions, Pennell sweet-talked him into giving away more information about the naval Enigma machine.49 Copies of these conversations were sent direct to Commander Denniston, and cryptographers Dilly Knox, Oliver Strachey and Frank Birch at Bletchley Park.50 On 8 January, May disclosed to Pennell:51
There are spare wheels kept in a box and they are easily inserted. The wheels are numbered and changed roughly every two days. The change takes approximately sixty seconds and the wheels can be put on the shaft in any order . . . The layout of the ‘stechus’ is given below:
1
2
3
4
5
6
7
8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
9
10
11
12
13
14
15
16
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
17
18
19
20
21
22
23
24
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
I remarked to May that our Enigma machine functioned very slowly and was unsuitable for urgent operation signals and consequently we used a table. He said that their Enigma was as quick as anything (I must confess it sounded quicker than our GG cypher when it is used by submarine officers).
May took a piece of paper and drew the German method of working with letters for codes. He explained that when a petty officer presses Z on the key and Q lights up, his opposite number writes it down in the corresponding column.
In turn, Pennell gained May’s trust by confiding in him about top secret British naval codes.52 The strategy was not risky because Pennell knew that May would not be going back to Germany until the end of hostilities and could not impart the information to the German navy. Pennell’s decision to befriend May proved correct. May would turn out to be one of the most important prisoners with knowledge of German naval Enigma. Pennell worked on the logical assumption that the German navy probably used an Enigma machine similar to that of the Royal Navy. The Naval Intelligence team at Trent Park continued to pump U-boat crews for information on Enigma and codes during 1940.53
On one occasion, pilot Wilhelm Meyer and wireless petty officer N125 chatted together about codes used by the German navy. It was N125 who inadvertently told Meyer:
Do you know the special U-boat morse code? This is used for rapping signals, when one is locked up anywhere. If you want to give a dot, you give a dot, and for a dash you give 5 dots. For instance, if you want to give your name, you give 5 dots twice, one dot, 5 dots, one dot, 5 dots, 5 dots, dot, dot, 5 dots, dot.54
John Godfrey (head of Naval Intelligence Division) recognised the value of the information being gathered at Trent Park and later wrote: ‘I have reviewed the results obtained from naval prisoners of war since the outbreak of war, and can unhesitatingly confirm that they are of such operational importance as to make it vital to develop this source of information to the full.’55
Information from the interrogation and secret recordings of U-boat wireless operators continued. This included operators from U-32 and U-31. Copies of their reports were sent to cryptographer Frank Birch at Bletchley.56 The close working relationship and sharing of intelligence between Kendrick’s unit and Bletchley continued for the duration of the war.57
PILOT WILHELM MEYER
In December 1939, 31-year-old pilot Lieutenant Wilhelm Meyer was transferred from the Tower of London to Trent Park along with U-boat prisoners. He had been amongst the first captured Luftwaffe pilots to be brought to the Tower, having been shot down over the river Thames on 20 November 1939.58 Pulled unconscious out of the freezing water, he had been taken first to the Royal Herbert Hospital for medical treatment because of injuries.59 Whilst at Trent Park, he was interrogated about the crew’s call-sign, wavelengths on radio transmissions and communication with ground control. His interrogation by Felkin was written up in a special report and sent to the Air Ministry.60 It confirmed for the Air Ministry that Meyer’s crew had received no navigational aid on their flight to England. They had flown by sight to just north of Borkum and then on a plotted course between Deal and Dover where they crossed the coast of England. Assistance for their return flight (had they made it) would have been given over shortwaves.
By the end of 1939, the unit began to give its prisoners codenames in the transcripts, such that it is often not possible today to identify the original prisoner (there are some exceptions), as in the case of Meyer. There was still much talk amongst the prisoners about U-boat production, torpedoes, minesweepers, U-boat tactics, the manufacture of German aircraft (Heinkels and Junkers) and belief that the war would end soon.61
In one conversation, a wireless operator commented to a German pilot: ‘What is the X-Gerät?’62 Pilot (A129) replied: ‘It has to do with dropping bombs on unseen target.’ This is thought to be the first reference to X-Gerät by any prisoner and its significance is discussed in the next chapter.
Another prisoner had bailed out on the island of Hoy (Scapa) on 30 November 1939 when his plane crashed, killing all other members of the crew. He revealed that he had really been flying in a Ju.88, not the He.111, a machi
ne that was little known in 1939. Felkin wrote: ‘The interrogator realised that this man was a born talker and kept him under interrogation – with excellent results – for 103 days.’63
On 23 December a conversation was recorded between Meyer, Ambrosius (German air force) and May (U-35) in which Meyer asked a somewhat rhetorical question: ‘Do you think listening apparatus are built in here. I don’t think so. It is the one thought that is always with me.’64
With the exception of Meyer, the other prisoners did not suspect that the place was ‘wired’. The conversation turned to their treatment by the British as prisoners of war. Meyer recounted how, when he had gained semi-consciousness after being pulled out of the Thames, he had asked for a cigarette and was given an expensive cigar. He told his mates: ‘When we were fished out of the water, we were undressed at once and firmly rubbed down, and everyone gave us a part of his linen, and then we got eggs and bacon. It tasted good. They are kind-hearted people after all.’65
May replied: ‘Damn this war! We might have been comfortably sitting at home now. But the English won’t rest until they have completely crushed us.’66 At nine o’clock that evening, Meyer was taken out of the room by a guard. Ambrosius was alone with May and piped up: ‘He is a very decent fellow.’ To which May replied: ‘I like him quite well. He is a man at least.’
Hochstuhl was one of the few prisoners who became suspicious of the reason for being held in the Tower. In a conversation recorded on Christmas Eve, he expressed doubts to Meyer about why he had been brought to the Tower, then released to a regular prisoner-of-war camp and brought back again:
HOCHSTUHL: I have had unpleasant experiences here. Even though the treatment is not too bad, I don’t trust these fellows any more. I don’t trust the quietness of it here: I have had my experiences in the Tower. They use all sorts of means here to get information out of us. I think it is despicable when they put English officers into German Air Force uniforms.
MEYER: Did they do that?
HOCHSTUHL: Yes, in the Tower . . . I am very sceptical about our being brought together just on Christmas Eve, for we are not generally so well treated. I don’t trust these people. They are doing it for some special reason.67
The reference to English officers being put into German air force uniform refers to the M Room’s use of stool pigeons to provoke specifically oriented conversations for intelligence needs.68 A report summarised the importance of stool pigeons:
A good stool pigeon could accomplish a great deal to help an interrogator. He could put the prisoner in the frame of mind best suited to the tactics upon which the interrogator was relying. And even the most difficult prisoners could, with continued briefing, conduct a complete interrogation. Not the least of his value lay in his ability to flatter a prisoner into giving a full account of a recent interrogation, as a result of which details given at the interrogation could be embellished and assessed for their accuracy.69
The use of stool pigeons is discussed in more detail in the next chapter.
On Boxing Day 1939, Meyer, Ambrosius and May passed the time playing cards. Their conversations that day were recorded as Special Reports No.9 and No.10.70 Talk was of naval and air force matters.
Meyer told May, ‘We must rely on the Air Force. When Hermann [Goering] sends all his Squadrons over at the same time, that will give them a surprise. And then perhaps the new Heinkel will be ready, with four engines.’
Meyer replied, ‘Our Air Force comrade (Hochstuhl) is a very queer fellow, he is suspicious of everybody, he even looked at me mistrustfully.’
May said, ‘All I should like to know is what they want me for. If they want to know anything about U-boats, then I haven’t the faintest idea. The officers are probably doing their duty, but we are not going to let ourselves be pumped.’
‘They are much too dumb anyway,’ Meyer replied.
The comment that their captors were ‘dumb’ was precisely what British intelligence wanted them to think.71 In believing that the British were incompetent, stupid or both, it enabled the M Room project to roll out successfully and undetected.
It appears from comments at this time that the prisoners were taken to brothels. May said: ‘We are going to that brothel next month.’ To which Ambrosius replied: ‘We shall probably frequently wish we were back here.’72
Ambrosius also commented: ‘It is surprising that they have not yet photographed us in case we should escape.’73 To which Meyer replied: ‘I would make for Ireland.’
Relaxed and quite complacent, the prisoners continued to talk about bombs, military strategy, German aircraft and U-boats:
MAY: We have more now – say, ten shipyards where U-boats are built – then two boats could be launched every week. But they are only just starting to build. There is the Germania shipyard in Kiel, the Deutsche Werke in Kiel – they have not yet built and should now be starting – then there are two shipyards on the Baltic. In Bremen, U-boats are built by the Deschimag, then building is going on in Hamburg by . . .
MEYER: Blohm & Voss.
MAY: Yes, and then they are building in Wilhelmshaven at the Siegmunds shipyard. They are also building in Kiel at the Kieler Kreigsmarinewerft. That is already six shipyards.74
These comments gave British intelligence an important insight into Hitler’s rearmament programme and piecemeal information that could be used to corroborate intelligence coming from other sources.
On 12 January 1940, Ambrosius was interrogated by Felkin. Immediately afterwards, he was placed in a room with Erich May. Ambrosius recounted his interrogation and told May that the interrogation officer had shown him poor-quality photographs of military installations and commented: ‘They must have poor apparatus. I told them so. They were taken from a height of 7 to 8 thousand metres. Our photos are better: when they are taken from, say, 4,000 metres, you can see every house on them.’75
The interrogation officer had then shown Ambrosius a selection of better-quality photographs of Kiel and Wilhelmshaven, taken from 3,000 metres. It led to Ambrosius speculating with May as to whether the British could successfully bomb German runways and installations based on such photographs.76
Apart from interrogation, British officers sometimes ‘befriended’ a prisoner if it was thought the softening-up process would reveal information. The prisoner might be taken for a walk and chat, or for an alcoholic drink alone in relaxed surroundings. The result of these friendly chats often came out in the conversations between fellow prisoners afterwards. The British officer might talk about politics and try to gauge the prisoner’s opinion on certain matters which might lead to him inadvertently giving something away. The intelligence officer might tell the prisoner that the Führer had not kept his word about having no design on Czechoslovakia.77 This was something that could not easily be refuted and such evidence of deceit was intended to plant doubt and criticism in the mind of the prisoner.
Captured German officer Lieutenant Fritz Wenzel found himself in a cell with his old comrade, Hans Engel; as former interrogator Matthew Sullivan recalled:
They had a great deal to say to each other and naturally took the precaution of talking softly and frequently changing position. They also had a good look around the walls, but despite the most meticulous search, they never succeeded in finding any trace of a microphone; so perhaps they were over-cautious. The brilliant device of incorporating a microphone in the electric light fitting was never detected by any prisoner.78
Prisoners were sometimes befriended at Trent Park:
The game played with him [Fritz Wenzel] was an hour’s pleasant walk in the park with a British naval officer . . . Wenzel of course giving nothing away – unless afterwards to the listening socket in the cell. Why otherwise was he at Cockfosters for a month? Not just so that he could catch up on his reading from the excellent library!79
In another case, a German armaments officer of a coastal unit was held in confinement almost exclusively with his interrogator who took him out,
for trips to arm
ament establishments near London and for meals in restaurants . . . The report on this prisoner, one of the few who really did not know he was being interrogated, became for the next six months the book of reference on bombs, fuses and aircraft armament. It was first learned from this officer with surprise that Germany had radar at the beginning of the war.80
The subtle demythologising of a prisoner’s confidence in Nazi Germany was a common tactic. Sullivan wrote of Felkin:
His favourite time of day was at night. Over a glass of whisky in Room A, which was fitted out like a sitting room, he would slowly convince a POW that Germany had lost the war. This he proved by taking the prisoner for a night out in London to show the German that the city, far from being in ruins, as Goebbels claimed, was bustling with activity and night life.81
Such excursions served as a subtle propaganda tool and were important alongside the gathering of intelligence to provoke the prisoner into questioning the Nazi leadership and whether Germans had been brainwashed. A prisoner might even begin to express his concerns about the Nazi leadership to his cellmate. When this happened, it confirmed that the various ruses being used by British intelligence were indeed working.
CHAPTER 3
Trent Park
The first prisoners to arrive at Trent Park comprised mainly U-boat crew and Luftwaffe officers.1 Relatively few army prisoners were captured during this first phase of the war; their influx did not gather momentum until after the successful British campaigns in North Africa in 1942. By the end of the first year of the war, Kendrick had submitted 1,533 reports, the majority emanating from the Air Intelligence section at Trent Park.2 The material was classified into categories Top Secret, Most Secret or Secret, determining who had the right to see it. Female staff undertook much of the clerical administration of typing up interrogations, summary reports, and Special Reports from bugged conversations.
Kendrick’s first intelligence report showed that the secret listeners had gathered extensive and detailed knowledge about Germany’s military capabilities.3 An appendix to the survey gave a comprehensive list of the main topics emerging from bugged conversations on which reports were available. They included aerial and magnetic torpedoes, aerodromes in German-occupied countries, armour, artillery, Austria, Bulgaria, British POWs, cavalry, conditions in Germany, enemy aircraft equipment, Gestapo, Goebbels, Goering, hand grenades, Himmler, Hitler, Hitler Youth, identification of [German] units, Jews, losses (army, German air force and navy), Mussolini, navigation on aircraft, parachute troops, Poland, production of enemy aircraft, rockets, ‘S’ boats, small arms, SS, strength of enemy armed forces, tanks, training of enemy forces, U-boats, weapons, Western Front, Zeppelin.4
