Northampton’s Wartime Spy Radio: Caroli and the Wrong Number

When MI5 distributed the captured spy radios after the war, the Northamptonshire Police received one. It was catalogued and displayed as belonging to Gösta Caroli. That attribution stuck—in books, in labels, in memory. But the radio itself tells a different story, if you know where to look.

Introduction

Gösta Caroli was one of the Operation LENA spies who landed in England on 5 September 1940. He was one of the pre-invasion spies and had been instructed to gather information on airfields in the Birmingham/Northampton area. He was equipped with a wireless radio, a transmitter/receiver combo, with which he could send his coded reports to the Abwehr in Germany. As with many of the LENA spies, things didn’t quite go according to plan.

The LENA spies were generally poorly equipped and poorly trained. Gösta had never practiced a parachute jump or a parachute landing. His flight crew advised him to drop his equipment on a separate parachute but he feared losing track of it. He decided to strap the wireless case to his chest, and his flight crew shrugged their shoulders. It was not a smart move.

After leaping from the aircraft, Caroli landed in darkness near the village of Denton, 5 km southeast of Northampton. One of the straps holding the radio in place broke and the case struck him on the chin, knocking him unconscious. He had landed on the night of 5 September and woke up on the morning of 6 September. Groggy, he gathered his gear and dragged it under a hedge where he passed out again. A farm labourer found him later that day, reported it to the local farm manager and… Gösta was taken into custody. He gave a statement to the Northamptonshire Police and was then transferred to MI5’s Camp 020. He was interrogated intensely and eventually agreed to work as a double agent and send doctored messages back to the Abwehr, under MI5’s watchful eye. His mental health was not the greatest, and after slitting his wrists in October and trying to escape in January, MI5 reluctantly admitted that Caroli was not double cross material. He was retired to Camp 020R (Huntercombe) and sent back to Sweden after the war.

Spy Radios

During the war, MI5 maintained meticulous lists of the possessions with which the spies arrived. Everything was a piece of evidence, and might be needed at a future criminal trial, and the chain of custody needed to be airtight. If an item had a serial number, or any identifying marks, it was noted on these lists. Josef Jakobs, for example, arrived with a wireless radio that had a small “26” marked in white paint on the upper right corner of the unit. His disc code was marked as “9”. Similarly, the colour of the small suitcase or attaché case containing the wireless set was often noted in the list of possessions. Some had a black case, others had a brown case. Some had leather cases, some had cardboard cases.

After the war, some of the espionage equipment was distributed to museums and archives across England. The Imperial War Museum, for example, has a wireless transmitter/receiver in a black case. It “probably” belongs to Drücke or Wälti but the white-painted number is covered by cables in the display case. The IWM also has transmitter #8 belonging to Kieboom and Waldberg.

The Edinburgh Police believe that they have a wireless set belonging to Wälti but it is quite clear that it belongs to double agent TATE (Wulf Schmidt). The type of wireless transmitter (in two separate case) and the identification numbers match TATE’s set, not that of Wälti. Clearly, whoever was dispersing wireless radios from MI5s vaults did not know that the equipment should actually belong to the spy captured by a specific police force.

Northamptonshire Spy Radio

Which brings us to the wireless transmitter/receiver held by the Northamptonshire Police. Up until a few months ago, I wasn’t even aware that they had a spy radio. I first came across it when I was grinding my way through transcribing and translating the Olsson and Jonason Swedish language book on Caroli. The authors included a photograph of the wireless set and the caption noted that “The radio that Gösta Caroli carried with him is today held at the Northamptonshire Police Museum. Photographer: Dick Cowley.”

A Clear Photograph on Facebook

Intrigued, I did a Google search for “Northamptonshire Police” and “Caroli” and ended up on Facebook, with two posts from the Sywell Aviation Museum page. One post had been written on 29 August 2019 and the other on 15 May 2023. Both detailed the story of Gösta Caroli’s landing and capture.

The 2023 post included a black and white photograph of his radio equipment (likely a historical photo from the Northamptonshire Police Archives) and a photograph of the statement made by Cliff Beechener, the farmer who apprehended Caroli. This post, entitled “How an Unconscious German Spy was Found in a Northamptonshire Cabbage Patch and his Radio Set is Still Held by Northants Police…” included a summary of Caroli’s story and then noted:

“Caroli’s spy radio (pictured) was kept by Northamptonshire Police and remains in their archive at Wootton Hall, Northampton. The [Sywell Aviation] Museum had been in contact with the Police for many years to try and secure it on loan for display. In 2022 they contacted us to offer it on loan – hooray we thought, we better check our insurance…. well it turns out that an original WW2 German Abwehr radio with unbroken provenance to a named agent is worth about £100,000. As such we had no option but to turn them down…”

The 2019 post included the same photographs but… buried in the 25 comments was a comment from David Bailey which read:

“I have copies of the documentation that followed his capture, from Dick Cowley. About ten years ago there was a visitor at FHQ who came to see Dick. It transpired that it was Caroli’s son, who had been unaware of the exact details of his father’s capture and had come to Northampton to get the “full story”.”

In the replies to this original message, David also uploaded a photograph of a wireless transmitter set with the note: “I have tried on a number of occasions, to add a photo. Just one more try: here’s a photo of the spy radio that Dick Cowley requested that I take.”

David Bailey is a former member of the Northamptonshire Police who, at the request of the former Northamptonshire Police archivist, Dick Cowley, took some photographs of the spy radio that the police have in their possession.

Clues: Pencil Marks and Crystal Frequencies

The photograph that David uploaded to Facebook is of very high resolution and provides an amazing amount of detail. One of the first things I noticed however, was the pencilled “24” on the receiver dial.

Caroli’s radio had been marked “35” not “24”. Was this pencilled “24” a wireless serial number or something else? Because normally, the serial number of the radio was marked in white paint on the upper right corner of the unit. In David’s photograph, however, the white painted number was obscured by a wire.

I emailed my amateur wireless radio expert, Thomas Hoeppe, and asked about the “24” on the receiver dial. He replied:

…I don’t think [the number on the scale disc] is a serial number. The inscription was always in one of the corners, done with the same white ink used for the lettering. I think the man who used that set marked a frequency. The scale from 0-100, spread over 180 degrees, indicates the receiving range. There was a calibrating curve, where you could read the frequency in kHz or MHz from scale reading or vice versa. The “24” is most possibly a mark, where a frequency was used more often, e.g. the “home station”.

That sounded quite logical to me, and yet I wondered… The picture in Olsson and Jonason’s book provides an excellent frontal view of the wireless set and, although the resolution is not great, I could almost convince myself that there was a “24” painted in the upper right hand corner. but the more I zoomed in on the image, the fuzzier it got. It wasn’t enough.

I dove into Josef Jakobs’ file, the one with which I am most familiar. Although his file does not contain a photograph of his wireless set, it does have a substantial write-up by a wireless expert. I came across this little tidbit:

“The receiver dial [of Josef’s wireless set] has the figure “26” pencilled on it which seems to be the serial number of the apparatus. The same number is to be seen painted in white on the back right hand corner of the transmitter panel.” (KV 2/26, folio 2a)

A few days later, more evidence came from Thomas’s colleague, Manfred Bauriedel, who examined David Bailey’s photograph more closely and noticed that the quartz crystal, plugged into the transmitter portion of the set, was marked 4508.5 kHz. Caroli’s working frequencies were 6100 kHz and 4108 kHz. Still… crystals could be unplugged and moved between sets. This happened with easily removable items like the batteries and Morse keys.

The Painted Number

What we really needed was a high resolution frontal view of the Northamptonshire wireless set! I reached out to David Bailey via Facebook. He replied within a few days. He had a number of high resolution photographs of the wireless set, which he emailed to me, along with the documents he had in his possession. The photographs are exquisite, of very high resolution, and one gave an almost full-frontal view of the wireless set. The pencilled “24” wasn’t as visible, washed out by over-exposure against the white receiver dial. But… painted in the upper right hand corner, with white paint, was “24”.

The evidence is conclusive: a white-painted “24” in the corner, a pencilled “24” on the receiver dial, a crystal at 4,508.5 kHz. All three point to the same agent — and it isn’t Caroli. The set in the Northamptonshire Police Archives belongs to Jan Willem ter Braak, born Engelbertus Fukken. “Unbroken provenance” to Caroli? Hardly.

Jan Willem ter Braak

Jan Willem ter Braak landed by parachute in early Novembrer 1940, near the village of Hanslope, Bucks. He is one of the very few agents to have escaped capture by the British authorities. He left his parachute and flying overalls behind, along with a wrapper for Belgian chocolate and vanished. Five months later, his body was found in a Cambridge air raid shelter. He had apparently shot himself in the head. MI5 tried to piece together his activities during those missing five months. He had managed to live undetected in Cambridge, despite the fact that his ration book was expired. The batteries of his wireless transmitter were drained, which led MI5 to conclude that he had been trying to reach the Abwehr. And yet, based on the information they gleaned, MI5 doubted that he had ever made contact during the daytime and had never tried during the nighttime. The unfortunate spy ran out of money and eventually out of time. He left his wireless case and suitcase in the cloak room at the local railway station and stepped off the stage.

The MI5 file of Jan Willem ter Braak also has an excellent photograph of his wireless set in its carrying case. One can see that the batteries and Morse key are different than with the Northamptonshire set. This seems to have been fairly common practice with MI5 possibly scavenging spare parts from unused wireless sets in order to support double agents like SUMMER and TATE. The photograph below also shows the lid of the case and there are noticeable marks on the upper part of the inside of the lid.

I did find one photograph of the Northamptonshire wireless set with its lid. It is clear that the lid has seen better days with several broken corners. The two short straps that hold the lid to the case are broken. What is noticeable however, is very similar markings on the upper portion of the inside of the lid. Perhaps there was a manufacturer’s label that got torn off, for the white bits do look like paper residue. Small manufacturing marks like this can be very distinctive.

One of the key documents appears in ter Braak’s MI5 file (KV 2/114) and provides a summary of the spies who brought wireless sets to England from the autumn of 1940 to the spring of 1941. Information on the double agents has been withheld but it is not difficult to figure out who is who. The type of wireless sets (S 88/5 vs SE 92/3) has been identified and provided by Manfred Bauriedel.

The wireless set used by ter Braak was labelled “24” according to his MI5 file. The photographs of his set, however, were taken at an odd angle and we cannot see the white-painted number. Although… if one zooms in on the white receiver dial and plays with the shadow/contrast/highlight settings… one can almost see the pencilled “24” on the receiver dial.

On Display as Caroli’s

In late August, Thomas, Manfred and I were batting ideas around and tracking down higher resolution photographs of the Northamptonshire Police set. Thomas decided to reach out to the Northamptonshire Police Archives, seeking some technical specifics on the wireless set. The current archivist, Sue Ward, replied and said the radio was actually not at the archives, but was on loan as part of a temporary exhibition at the Northamptonshire Museum & Art Gallery. The exhibition opened on 20 September 2025 and quickly drew outside attention. Today, if you search for “Caroli” and “Northamptonshire,” you’ll find a number of recent articles about the set.

The BBC and the Northampton Chronicle and Echo both published articles about Gösta’s set being placed on display. The Northamptonshire Museum has a write-up on the set, also attributing it to Gösta. Misattributed though it may be, the Northamptonshire Police have at least ensured the set survived and is still on view today. The renewed attention makes it all the more important to set the record straight.

Conclusion

After the war, MI5 distributed various pieces of spy equipment to museums and archives. The Northamptonshire Police received a wireless set in a carrying case, which they believed had belonged to Gösta Caroli, the spy they apprehended in September 1940. By then, the officers who had captured him were gone or reassigned, and the police took the attribution at face value: MI5 said it was Caroli’s set, so it must be his.

The evidence tells a different story. This set carries a pencilled “24” on the receiver dial, a painted “24” on the transmitter, and a crystal stamped 4,508.5 kHz. Caroli’s set was labelled “35” and operated on different frequencies. All three clues point instead to Jan Willem ter Braak (real name Engelbertus Fukken), whose file confirms his set was numbered 24 and tuned to 4,508.5 kHz.

That raises uncomfortable questions. If Northampton’s set isn’t Caroli’s, where is #35? How many other spy radios sit mislabeled in collections? We already know the Edinburgh Police have misattributed TATE’s set to Wälti. To Northamptonshire’s credit, their preservation kept ter Braak’s set from vanishing altogether. The misattribution lies in MI5’s muddled handling of captured equipment—sloppy even during the war, when pieces of evidence were misfiled or misplaced—not in Northamptonshire’s stewardship. Thanks to the release of MI5 files at Kew, the evidence strongly indicates that the Northampton set belongs not to Gösta Caroli, but to Jan Willem ter Braak.

Sources

Sywell Aviation Museum Facebook Page – post dated 2019 August 29 – How an Unconcious German Spy was found in a Northamptonshire Cabbage Patch

Sywell Aviation Museum Facebook Page – post dated – 2023 May 15 – How an Unconcious German Spy was Found in a Northamptonshire Cabbage Patch and his Radio Set is Still Held by Northants Police…

Northamptonshire Museum site – Histories of Northamptonshire – article on the Caroli spy radio

Northampton Chronicle and Echo – Nazi spy radio seized by Northamptonshire Police during World War Two to be displayed at Northampton museum

BBC – Gösta Caroli’s radio goes on display – Nazi spy Gosta Caroli’s radio goes on display in Northampton

Northamptonshire Police Facebook Page – Gösta Caroli’s spy radio going on display

Header image from Sywell Aviation Museum Facebook page.