So far emphasis has been laid on German activities against us and little or nothing has been said as regards the Swiss, who after all were somewhat concerned, because though the organisation was not directed against Swiss interests we were to some extent abusing Swiss hospitality by our activities. Also, as a last resort, if kidnapping and strong-arm methods failed, the Abwehr could always tip off the Swiss and have us arrested by the Bupo, which would at least liquidate a portion of the network. This was not, however, necessary, as the Swiss had not been inactive.
The Swiss had an efficient monitoring system and it subsequently transpired that they, like the Germans, had been monitoring our traffic for some time. Their original information, however, came from a casual source - or so I was told by the Swiss police after my arrest.
At some time, it must have been a year or so previously, one of the wireless staff at the Geneva airport had been casually twiddling the tuning dial of his set. No planes were due in and he had no signals to listen to and was looking for something on the short wave with which to lighten his boredom. Suddenly he picked up a strong signal transmitting in Morse but in code and using amateur procedure. This intrigued him as all amateur radio transmissions had been forbidden in Switzerland since the outbreak of war, and anyway an amateur transmitting five-figure groups was somewhat more than unusual. He noted the call sign and frequency and reported the matter to his superiors, and the report finally filtered through to the Bupo and the army.
The station was monitored and in due course by D.F. they discovered that it was located in Geneva. In the course of their investigations they came across another set, also working from the town and using a similar procedure. These sets were, of course, those of Bolli and Hamel. At that time the Swiss police were under the impression that these were either British transmissions or possibly a local Communist network working into Germany. It seems likely that at the same time they also picked up my transmissions from Lausanne and monitored them as well.
Exactly why the Swiss took no action for a period of at least a year, and only started offensive action against these sets in the autumn of 1943, I do not know. It is possible that they were hoping to get enough traffic to enable them to break the cipher, or it may be that they were unwilling to take action against sets which they thought were being worked by the Allies. Indeed they might never have taken action against them unless pressure had been brought to bear by the Abwehr, who could and may have given them the facts. The only people who can answer that question are the Swiss police and the Swiss General Staff. The fact remains that it was not till the autumn that any serious action was taken- and this speedily proved successful.
Mobile D.F. vans were ordered into action but it was not easy to locate the exact whereabouts of the two Geneva transmitters, as they were in a built-up area (which was the precise reason why they had been put there by us). When the vans had pinpointed the two transmitters to a comparatively small area, another technique was brought into play, one which was originated, I believe, by the Germans and used with much success to locate Allied transmitters working in occupied countries. During the time that the sets were on the air they cut off the current from each house in succession. When on pulling the switch the set went off the air they were certain that they had identified the house in which it was located. This they did, in turn, with both Bolli's and Hamel's transmitters.
On October 9 I was sitting in a cafe drinking my morning cup of coffee when I saw in the first edition of the Tribune de Geneve a small announcement that a secret short-wave transmitter had been discovered in Geneva and its operators arrested. This item was removed from all subsequent editions of the paper and it was mere chance that it caught my eye. That night I heard the Centre vainly calling the Hamel transmitter, and feared the worst. The next morning my telephone rang and I heard Rado's voice at the other end. "You will be sorry to hear that Edward is much worse and the doctor has been called in. He decided after consultation that the only thing to do was to take him to hospital." I made suitable sympathetic noises to keep up the pretence, but my mind was working furiously. This meant that the only firm link with the Centre was my transmitter, with the possible doubtful use to which we might put Bolli's (here I was overoptimistic). Rado's agitation, though suitable to the tenor of the conversation, was also perfectly genuine. With the "doctor" looking after Hamel, Rado felt the "hospital" looming unpleasantly near for him also.
A day or so later he telephoned me again and said that he was coming over to see me in my flat under cover of darkness, a thing he had never done before and an action symptomatic of his agitation. He arrived and told me that not only had the Hamels been arrested but the police had also simultaneously raided Margarete Bolli's flat and arrested her as well. Hamel had been caught flagrante delicto, sitting working the transmitter; Margarete had been caught equally in the act but in rather a different sense as she had been found in bed with Peters, the Abwehr agent, who had succeeded only too admirably in his task of getting into the girl's confidence. A complication, slightly embarrassing to the Abwehr, was that Peters had been arrested also as an accomplice!
We never understood why the Swiss, having held their hands so long, acted in the end with such precipitancy.
They had not kept the buildings under observation; but if they had they could have scooped the whole gang, including Rado. As it was, Rado had a narrow escape as he went round to see Hamel a few hours after his arrest and while the police were still searching the flat. Luckily he happened to glance at a clock which Hamel kept in his shopwindow and the hands showed danger. It had been agreed that the hands of the clock should show midday when all was clear. During transmission times or if danger threatened the hands were changed to some other time. As Hamel was transmitting at the time of his arrest the signal showed danger, and Rado was warned before he knocked and fell into the hands of the police.