The Irish and British governments have for the first time conducted a joint exercise testing how they would respond together in the event of an attack on the undersea cables in the Irish Sea.
The scenario, played out on Wednesday, simulated disruption to multiple communication cables in the Irish Sea, at a time when Russian activity in the waters of Europe has been ramped up.
An attack by the Russians, by cutting or otherwise sabotaging the undersea cables, is seen as a major risk to Irish, European and US communications.
The simulation on Wednesday was a desktop exercise – code-named Eastern Pearl – rather than involving any vessels at sea.
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However, future exercises joint Irish-British exercises are expected to become more complex as Ireland and Britain seeks to position themselves against Russia’s efforts to intimidate and disrupt European nations, most of whom are supporting Ukraine in its war with Russia.
[ Nato allies say they foiled Russian subsea cable sabotage plotOpens in new window ]
The co-operation between the two countries arises from an agreement being reached at the Irish-British summit in Cork in March 2025, when an updated defence agreement to protect critical undersea infrastructure was signed.
However, while Wednesday’s exercise was limited to a desktop-based simulation, it was regarded as significant as it was the first of its kind involving Ireland and Britain.
It involved the Department of Culture, Communications and Sport and the UK’s department for digital, culture, media and sport.
Minister Patrick O’Donovan said the exercise marked a “key milestone” in the development of enhanced co-operation between Ireland and the United Kingdom “in preparing for disruption to our shared critical undersea infrastructure”.
“Strengthening partnerships and working relationships with our neighbours will be key to improving the resilience of the network of international subsea telecoms cables serving Ireland, the UK and Europe,” he added.
Eastern Pearl formed part of the commitment outlined in the UK-Ireland 2030 programme agreed by the Taoiseach and UK prime minister last year to strengthen co-operation in the area of critical undersea infrastructure.
So-called “shadow fleet” oil tankers have been tracked in the waters off Ireland in recent years, through the Irish exclusive economic zone. Vessels carrying sanctioned Russian oil are increasingly opting to travel around Ireland instead of taking the quicker and safer route to the English Channel.
This follows an announcement in May by the British government that the royal navy would begin seizing shadow-fleet vessels passing through the channel.
There is no law against ships travelling through another country’s exclusive economic zone. However, the British government said shadow-fleet vessels are effectively “stateless”, meaning they can be legally boarded and seized in international waters.
The Irish Government has also signalled it intends to start inspecting such vessels and legislation is being drafted to grant the Naval Service additional powers to board ships at sea.
