This paper examines the challenges that the National Health Service poses as an environment for public key cryptography systems. The NHS is Europe’s largest single employer, with over 1.2 million staff. It provides lifetime healthcare for most of its population, and has done so for 55 years. In the last decade, it has launched several major programmes to develop NHS-wide information systems. Just the scale of the NHS is daunting. But systems that handle patients’ medical records are subject to a plethora of laws, policies, guidelines and practices for controlling the access, use and storage of the information. Taken together, the rules are complex and sometimes contradictory and, in addition, must be balanced against both patients’ express wishes and their clinical needs. Cryptography is an obvious means to secure and protect confidential information. Recently, identity-based public key cryptography schemes not only seem easier to deploy than previous schemes, but also seem equal to the challenges. In this paper, we give a detailed overview of the features and challenges that the NHS environment presents to uses of cryptography, to qualify our impressions of our cryptosystem and to guide our future efforts to develop it.