Tony Blair refused to share sensitive intelligence linked to Sellafield, citing the need to protect sources and the lack of guarantees about who could access it.

MI5 warned that sharing could not ensure access control or confidentiality, reinforcing the government's stance against direct intelligence sharing with Ireland on Sellafield threats.

The issue sits within broader post-Good Friday Agreement dynamics, with Irish focus on Sellafield rising and reflecting wider Ireland-UK relations and domestic pressures.

Ambassador Sir Ivor Roberts noted increased Irish pressure and legal challenges regarding Sellafield, driven by post‑agreement relations and internal political rhetoric.

Irish Prime Minister Bertie Ahern pressed for intelligence-sharing with the UK about threats to Sellafield in the wake of the 2004 Madrid bombings.

Declassified files reveal Ahern urged Blair to consider secure, yet possible, information-sharing arrangements on potential Sellafield threats.

Ireland was offered assurance that the British ambassador would brief Irish officials if a Sellafield threat emerged, rather than direct intelligence-sharing.

Shantha Shan of Patricia Hewitt’s private office described Ireland’s determined push for information and the UK’s firm stance against releasing it.

Ahern argued that protecting lives and health should take priority over source confidentiality, seeking secure ways to share sensitive information.

The episode highlights broader tensions between Ireland and the UK over sensitive security information and governance of Sellafield on UK soil.

Blair promised that any real Sellafield threat intelligence would be shared as fully and quickly as possible, within the constraints set by intelligence originators.

The Department of Trade and Industry confirmed MI5 and the Security Service were uncomfortable with sharing terrorism-related intelligence with Dublin.