Well, not necessarily a national emergency. Identifiable data can be released if it is approved by the Confidentiality Advisory Group (these people: http://www.hra.nhs.uk/about-the-hra/our-committees/section-2...). You can see a list of approved studies here http://www.hra.nhs.uk/about-the-hra/our-committees/section-2... , it seems they approve about 30 applications per year.