GB0GLS is a special event station to commemorate the role played by the work of the Radio Security Service in Northern Ireland during WWII. In particular, GPO Gilnahirk Listening Station manned by the civilian staff of the General Post Office (GPO). We also remember the work of our local Voluntary Interceptors who also made a valuable contribution to the listening operation.

Gilnahirk, just five miles from Belfast city centre, was one of several WWII, “Y” or Wireless Listening stations. To be more specific, Gilnahirk was a product of a War Office directive to strengthen the work of the civilian GPO Illicit Wireless Intercept Organisation (IWIO) in a time of war or national emergency. Targeting specifically a possible threat from spies and other hostile agencies, the work of the IWIO would fall under the jurisdiction of Military Intelligence. Unfortunately, MI5 who were responsible for Home Security wanted nothing to do with a purely civilian organisation.

Overcoming this hurdle was resolved by the War Office who created the Radio Security Section a sub division of MI8c. Through time the word “section” was replaced by the word Service. From day one the RSîS would control and direct the work of the GPO.

Prior to the construction of Gilnahirk the work of the GPO IWIO in Northern Ireland was conducted from GPO Ballygomartin Radio Station. With the switch on of GPO Gilnahirk in May of 1940 the work of the IWIO at Ballygomartin ceased, and the station returned to its normal peacetime role, under wartime conditions.

Supporting the IWIO work of the GPO from 1938 onwards, a select group of ex-service, ex-merchant marine and ex-commercial operators were enlisted as part time listeners across the whole of the UK. With the need for as many listeners as possible, an approach was made to Arthur Watts the then president of the RSGB with a view to recruiting radio amateurs from within its ranks across the whole of the UK. Once recruited these part time listeners became known as Voluntary Interceptors or VI’s and also fell under the control and direction of the RSS.

At the beginning of 1942 the work of the RSS in Northern Ireland was well established and being conducted by two separate groups of listeners. 1. The fulltime professionals of the civilian GPO and 2. the Voluntary Interceptors, the majority who were recruited from within the ranks of the amateur radio fraternity.

When the Allies began to plan for the invasion of Europe in 1942, steps were taken by the Director of Military Intelligence to tighten security across the whole of the “Y” Service including the Radio Security Service. Removing the fulltime civilian operation and bringing it under total military control meant that by October 1942 the GPO wireless station site at Gilnahirk was now officially Station No 4, of the RSS. At a higher level, Station No 4 was part of Special Communications Unit No 3 which was itself a sub division of MI8c. No longer a civilian operation, with everyone subject to Kings regulations and wearing a Royal Signals uniform.

Station No 4 closed in 1946, but in 1947 GCHQ restored the site for its post war / cold war listening operations. The WWII facilities were replaced in 1952 with a new state of the art station and this remained in service until 1978. Today nothing remains of original site.

In 2011 Her Majesty Queen Elizabeth II unveiled a memorial at Bletchley Park to the work of the Out Station which supplied Bletchley Park with raw signals intelligence and other services. Among the many names on this memorial is that of Gilnahirk.