Yes, the US and the UK maintain a sophisticated biometric data-sharing agreement that has been fully automated as of 2026. Under the "Migration 5" (M5) framework, which also includes Canada, Australia, and New Zealand, fingerprints of asylum seekers, nationality applicants, and individuals flagged for immigration violations are checked against international databases in real-time. This system is designed to prevent "identity fraud" and detect individuals who may have been deported from one country while attempting to enter another under a different name. While standard tourists on an ETA or ESTA are not subject to a "blanket" fingerprint check against every database for every entry, their biometrics are stored and can be manually cross-referenced if there is a security concern or a discrepancy in their travel history. This digital perimeter ensures that the "Special Relationship" extends to high-level border security and counter-terrorism efforts.