Ireland and the United Kingdom have carried out their first joint exercise focused on responding to a potential attack on critical undersea communication cables in the Irish Sea. The desktop simulation, code-named Eastern Pearl, tested how both governments would coordinate if several cables were disrupted amid growing concern about threats to European infrastructure.
The exercise is the latest development in closer Irish-British security co-operation and reflects the importance of subsea cables to communications between Ireland, Britain, Europe and North America.
What happened in the Eastern Pearl exercise?
Eastern Pearl took place on Wednesday, September 30th, 2026. It simulated the disruption of multiple communications cables in the Irish Sea, but did not involve ships, naval activity or an incident at sea.
Instead, officials worked through a desktop scenario designed to examine decision-making, information-sharing and co-ordination between the two governments. The exercise involved Ireland’s Department of Culture, Communications and Sport and the UK department responsible for digital, culture, media and sport.
No real cable attack was reported. The exercise was intended to test preparedness rather than respond to an active emergency.
Why subsea cables matter to Ireland and Britain
Undersea telecoms cables carry vast quantities of international data, including internet traffic, financial transactions, business communications and public-sector services. Damage to several cables could create disruption even if domestic networks remained operational.
For Ireland, which relies heavily on international digital connectivity, resilience in this area has implications for:
- Internet and telecommunications services
- Cloud computing and data-centre operations
- Financial and commercial communications
- Government and emergency services
- Connections between Ireland, Britain, Europe and the United States
A serious incident could require traffic to be rerouted through other cables and networks. The practical impact would depend on the number of cables affected, the location of the damage and how quickly repairs could be arranged.
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Ireland-UK agreement set the groundwork
The exercise follows an updated defence agreement signed at the Irish-British summit in Cork in March 2025. That agreement included stronger co-operation on protecting critical undersea infrastructure.
Eastern Pearl also forms part of the commitment in the UK-Ireland 2030 programme, agreed by the Taoiseach and the British prime minister, to improve collaboration in this area.
Patrick O’Donovan, the Minister for Communications, described the exercise as a key milestone in developing closer co-operation between Ireland and the UK. He said stronger partnerships would be important to improving the resilience of international subsea telecommunications cables serving both countries and the wider European network.
Russian activity and the wider security concern
The exercise took place against a backdrop of increased concern about Russian activity in European waters. Governments and security agencies have warned that subsea infrastructure may be vulnerable to sabotage, accidental damage or deliberate interference.
The source of any future incident would need to be established through evidence and investigation. Wednesday’s simulation did not identify an attack or attribute responsibility for any real-world damage.
Officials are also monitoring so-called shadow-fleet oil tankers, including vessels linked to the transport of sanctioned Russian oil. Such ships have been tracked in waters off Ireland, including within the country’s exclusive economic zone.
What happens next?
Future Irish-British exercises are expected to become more complex. The first simulation focused on government co-ordination, while later exercises could involve broader operational planning and additional agencies.
Both governments face practical challenges in preparing for a cable incident, including:
- Detecting unusual activity near subsea infrastructure
- Sharing information quickly across jurisdictions
- Assessing damage and prioritising repairs
- Maintaining communications while capacity is reduced
- Co-ordinating any maritime or law-enforcement response
The Irish Government has also indicated that it intends to inspect certain vessels and is preparing legislation that would give the Naval Service additional powers to board ships at sea. Any such measures would need to operate within national and international law.
Frequently asked questions
Was there an actual subsea cable attack?
No. Eastern Pearl was a planned desktop exercise simulating a possible attack and disruption to multiple cables.
Which countries took part?
The exercise was conducted by the Irish and British governments, with relevant departments responsible for communications and digital infrastructure involved.
Why is the Irish Sea important?
The Irish Sea contains infrastructure connecting Ireland and Britain, while those networks form part of wider communications routes linking Europe and North America.
Will the public lose internet access?
There is no indication of any current disruption. The exercise was designed to improve preparedness for a future incident, not to announce an existing outage.
Why this matters for Ireland today
The Eastern Pearl exercise shows that critical infrastructure protection is becoming a central part of Ireland’s national resilience planning. Much of the digital economy depends on systems that are physically located offshore and can be difficult to inspect or repair quickly.
For readers, the immediate message is that no attack has been reported. The longer-term message is that Ireland and Britain are building joint plans to manage a serious disruption if one occurs.
This first Ireland-UK subsea security exercise is an important preparedness step, but it is only the beginning of a broader effort to protect the networks that keep Ireland connected to the world.
