News Article

GCHQ experts to appear on The One Show

Last Updated: 23 Mar 2015
Marking the centenary of the First World War, GCHQ has been working with the BBC to show how the British brought secure communications to the trenches in 1915 through the development of the Fullerphone.


fuller phone
© IWM/Cat:Q27038

News article - Updated - 23 Mar 2015

During the First World War, military messages relied on a complex web of trench telephones. Messages sent by soldiers at the front, or officers from their HQ miles to the rear, typically travelled along cables. The Western Front became strewn with them.


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The trenches at Trench Farm, Suffolk, where filming with the One Show took place

The cables that connected these telephones were earthed by metal stakes driven into the ground and it was through these stakes that the messages leaked, fanning out into the ground, making it possible for the Germans to literally listen to the British voice messages as they leaked into the mud.

By 1915 it was clear that the Germans appeared extraordinary well informed of Allied plans. Raids were met by hostile fire precisely timed and directed. Relieving troops would be greeted, if not by shells, by shouts of welcome from the opposing trench!


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The scene is being set...

In response to this a young signals officer, Captain Algernon Clement Fuller, developed a new communication system that was more resilient to interception. He did this by making the signals that leaked into the ground less distinctive and more likely to be missed by an eavesdropper.

By stopping the Germans intercepting messages, the Fullerphone returned security to the Army’s communication network and gave the British Expeditionary Force a crucial advantage as the war progressed.

The principles behind the Fullerphone used technology that was developed in the Victorian era. It was radical innovation that applied old technology to a new problem. The Fullerphone remained in use until the end of the Second World War.


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The One Show Film Crew

Presented by Gordon Corera, The One Show item will show experts from GCHQ staging a demonstration of the early field telephony system, showing why it was susceptible to interception by the Germans. It will go onto discuss how the problem was overcome by Captain Fuller through the development of the Fullerphone.

Filming took place back in July 2014, and this item is expected to be broadcast on The One Show on Wednesday 25 March between 1900-2000 on BBC One.