The story of Signals Intelligence 1914-2014

Last Updated: 20 May 2016
When UK Signals Intelligence began in 1914, the world was a very different place. Read about the dilemma of the Zimmermann telegram, Signals Intelligence trailblazer William Green Swanborough, the intelligence officer and the movie star, and the capture of a spy in Rome in 1945.

The historical context

The pace of change in communications technology means that GCHQ constantly faces new challenges.  We need an innovative workforce able to keep up with technology trends if we are to continue to keep Britain safe and protect the government's official communications.  This is an enduring aspect of what we do, and was as true in 1914 as it is today.


The invention of British Sigint, 1914

If the War Office's preparations for making use of Signals Intelligence in wartime were minimal, there was even less consideration in the Admiralty.  One member of the Naval Intelligence Division, Fleet Paymaster Rotter, had devoted some time and effort in an attempt to break encrypted German Naval messages between 1910 and 1912. His lack of success only served to confirm the gloomy predictions of senior officers that encrypted messages would never be read.

Although the story told of British Signals Intelligence in the First World War focuses mainly on the work of Room 40 in the Admiralty, it was in fact MO5b (later MI1b), an intelligence section in the War Office which had the first success against German codes.  This was largely due to the fact that the French, who had years of experience of Signals Intelligence against the Germans, were prepared to share all that they knew.

MI1b did not really develop as an integrated Signals Intelligence Centre as the Army preferred to have units exploiting intercepted communications locally, at the General Headquarters on each of the Fronts.

Soon after the outbreak of war, Sir Alfred Ewing, Director of Naval Education, was invited by the Director of Naval Intelligence to lead the Admiralty's effort against enciphered German naval communications in Room 40.  He drew together a small team of German speakers.  Although they had no initial success against German encryption, their work in sorting and classifying the intercepted messages they received laid the foundations for traffic analysis.  This would prove eventually to be as valuable a tool for Signals Intelligence as for those trying to break encrypted communications: intelligence was produced by studying the external signs showing the way in which the Germans communicated.

Room 40's work to break encrypted communications was also kick-started into success by an ally: the Russian Navy found copies of the German High Sea Fleet codebook on a German Light Cruiser, the Magdeburg, and sent one to London.  After a few days' work, the system used by the Germans to re-encipher the messages was worked out and Room 40 began to provide a quick turnaround service of decrypted messages.


Magdeburg Code Book
© Crown Copyright 2014/TNA - ADM 137/4146

Although both the Admiralty and War Office were producing decoded German messages by the end of 1914, their Signals Intelligence organisations were still immature.  The need to protect this valuable new source of information was felt to outweigh the value of using it: the Battle of Jutland might have been a decisive victory for the Royal Navy if its commanders at sea had access to the same information as Room 40 had.  And the experience of codebreaking had no immediate effect of improving the security of the Royal Navy's or Army's own communications.  

Nevertheless, we can look at the Admiralty and War Office as they stood at the end of 1914 and see the first shoots of what would become a permanent Signals Intelligence organisation in 1919 and grow into the GCHQ of today.


The Zimmermann Telegram, 1917

Intelligence is only of value if you can actually do something with it, but reacting to information you have gathered could alert the enemy and cause communication methods to be changed. There is always a delicate balance between using intelligence and protecting the source. 

The story of the Zimmermann Telegram illustrates this well. 


Zimmer Coded


Zimmerman Telegram


In January 1917 the German Foreign Minister, Arthur Zimmermann, was concerned that an upcoming change in German policy could lead to the US being drawn into the war to help the Allies. He was aware that the impending declaration by Germany of unrestricted submarine warfare in the Atlantic would likely lead to the sinking of American merchant ships, and this would push the US closer to joining World War One on the Allied side. He hatched a plan to counteract this possibility by distracting America with problems on her Southern border.

Zimmermann sent a telegram to the German Embassy in America for onward transmission to their Ambassador in Mexico for him to share in time with the Mexican Government. The hope was his message would persuade the Mexicans to join the war on Germany's side, side-track the US with trouble close to home and postpone the transportation of American supplies to the Allied powers. In the telegram Zimmermann promised to support Mexico in the reincorporation of Texas, Arizona and New Mexico after the victory over the Allies. 

The telegram was highly sensitive, Germany encrypted it and never dreamt it would be read by anyone other than the intended recipient.  It was, however, intercepted by the UK and subsequently decrypted in Room 40 of the Admiralty, the section in the Admiralty which had started producing intelligence from intercepted and decrypted messages.

The value of the message was obvious and disclosing the content would greatly help turn opinion in the US against Germany but it would also expose the UK's code breaking ability.  A plausible cover story was concocted. A mysterious agent based in Mexico was invented and took credit for acquiring a copy of the message to mask the real capability in Room 40 that had done the hard work.

The telegram was shared with the US President and subsequently made public. When Germany began its submarine campaign and US lives were lost, public opinion in the US was swayed against Germany. The Zimmermann Telegram was one of the factors which persuaded American public opinion to abandon neutrality and enter the war against Germany.

Nearly a hundred years later, the story of the Zimmermann Telegram sheds light on a dilemma which is as applicable to today's GCHQ: the value of intelligence comes from being able to use it, but using it risks alerting adversaries to the vulnerability of their communications.  Ensuring that the use and protection of Signals Intelligence are in balance is still of vital importance today.

A Signals Intelligence trailblazer, 1918-1964

When most people think of the stars of Signals Intelligence history, they think of the men and women at Bletchley Park  who worked during the Second World War to crack enemy codes and provide Britain with vital intelligence. They will think of Alan Turing or Dilly Knox.

William Green Swanborough is a lesser-known name, but one who set the scene for those who came after him and was in his own way one of the most important figures in British Signals Intelligence history.


Swanborough Leiston Suffolk 1918
© Crown Copyright 2014


Swanborough joined the Signals Service of the Royal Engineers as a Self-Trained Radio Operator.  He served in the UK before receiving notice of being posted overseas on 13 November 1918. By December 1919 he was in India after re-enlisting for 3 years as a Wireless Telegraphist in the Indian Royal Engineers Signal Service. From India he was ordered to Kabul to support Sir Henry Dobbs' mission there to establish diplomatic relations with Afghanistan.

He left the Army and went to Port Sudan for a brief period as Superintendent of the Wireless Station, but then enlisted in the Royal Air Force (RAF). He was specifically charged with forming, training and managing the intercept station which Lord Trenchard had decided to establish at Mere Branston. The station was stood up formally in 1927 and marked the founding of RAF Signals Intelligence.

In 1931 Swanborough went to Estonia to negotiate an agreement with the Estonians to swap UK expertise for valuable Estonian intercept. He taught the Estonians the principles of Signals Intelligence against military targets: the need to identify networks and work out the hierarchy of individual units, the importance of understanding routine so that out of the ordinary activity would be immediately obvious and the need for continuity. He returned to the UK with an agreement that the Estonians would forward the encrypted Soviet military traffic they had access to. This material was sent to the UK right up to the outbreak of war.

After his return to the UK, Swanborough was commissioned. He moved the Signals Intelligence operation to RAF Cheadle in 1937 and commanded the station throughout the war, overseeing its massive expansion and the growth of a series of satellite stations. He was promoted Wing Commander in 1943.

After the War RAF Cheadle remained as the Air Ministry's main civilian collection site until 1964, when all the service ministries' civilian interception sites became part of GCHQ. Swanborough left the Air Ministry and became the first GCHQ civilian officer in charge of the station at Cheadle in January 1964. He retired shortly afterwards that same year with a record period of 37 years in charge of a station. He died in 1979, aged 80 and left behind a legacy that included laying some of the foundations for British Signals Intelligence.


The Intelligence Officer and the movie star, 1944

If you were asked to think of a glamorous career, Signals Intelligence probably would not be top of your list but as our next story proves, you never can tell who you might run into in this field of work.

Ron Challen worked in a Special Liaison Unit (SLU). The SLUs were run by MI6 and were responsible for ensuring that the most senior commanders in the field during World War Two could have access to the intelligence being produced in Bletchley Park. His first assignment was to General Eisenhower’s Headquarters in Algiers.

He was transferred to Taranto, Italy, to supply intelligence to the Commander-in-Chief of the Mediterranean, and subsequently became attached to the headquarters of the US 7th Army which was the lead formation for the invasion of the South of France in August 1944. By the end of that year he was ordered to form a new SLU in Australia. Let Ron take up the story.

"I told General Patch that I would have to leave in a couple of days, just as soon as a replacement arrived. He said he had so appreciated the Ultra intelligence coming in day by day that we must celebrate my exciting transfer. He invited me to a party arranged for the following evening.


Marlene Dietrich
© Wikimedia Commons 2014


"'Only fourteen people will attend', he said. 'Twelve 3-star and above Generals plus yourself and a lady, Contessa Maria von Losch. She will sit on my right and you on her right,' he said. 'You will recognise her as Marlene Dietrich, the film star. She is to entertain the troops tomorrow.'

"It was a fantastic affair held in a small marquee - a full Thanksgiving dinner with turkey and all the trimmings and unlimited supplies of French wine.

"Suddenly the lights failed and we were plunged into darkness. I felt Miss Dietrich's hand fumbling in my lap and the two of us held hands until the lighting was restored.

"It did nothing for me. She was old enough to be my mother and her repertoire of filthy jokes and bawdy songs was off-putting. I can truthfully boast, though, that I once held hands with Marlene Dietrich in the dark!"


The capture of a spy in Rome, 1945

 John Wright was in charge of a small Signals Intelligence unit which operated in Rome after its liberation.  His task was to locate enemy agents who could be discovered from their wireless transmissions. Here he recounts the story of the discovery of one of them.

"At the end of January 1945 it became known to us that there was another wireless agent for The Abwehr, a German Military Intelligence organisation, operating in Rome. The agent was known as Toppa and he had succeeded in establishing his station and was passing back reports to Germany.

"At the beginning of March, we got an indication of the quarter of Rome in which he might be operating, and a local watch in the area was started on March 14th.  No details at all were known of his wireless schedule. In these circumstances all that it is possible for the watch to do is to keep a constant ear open for any signals which sound local; it is a great operating art to be able to differentiate between a wireless signal that is merely loud and one that is both loud and local.


John Wright
© Crown Copyright 2014


"Such a local signal was heard on March 19th and was identified as part of a series of transmissions that had been intercepted for some weeks, without being identified.  On examining the back records of this series of transmissions, it was found that on a single occasion the reply station had used the emergency callsign 'TPO'.  As it was the habit of agents to choose the letters of their emergency callsign from among the letters forming their cover-name it was considered certain that the series of transmissions belonging to Toppa had been identified.

"Toppa was next active on March 23rd.  Sites for the two direction finding parties had been chosen near the Porta Ardeatina and on the Palatine Hill.  Both parties obtained bearings and these intersected in the street where it was already believed that Toppa might be located.  One of the vehicles had time to pass down this street and found that signals were loudest outside a particular block of flats.

"It was known from the interception of the previous transmissions that the next appointment was due on March 26th and a raiding party was accordingly arranged for that date.  Toppa came up on time and the block of flats outside which the signals were strongest was entered. The peak point of signal strength was found to be on the seventh floor and the suspect flat was entered.

"The German agent Toppa was found sitting there in a darkened room with his transmitter and the message he was sending laid out in front of him on a stool. The mains supply was immediately disconnected so that no more signals could be sent."

John Wright and his team of Signals Intelligence operators had caught the spy in Rome and stopped him from leaking more information back to Germany.