The loss of 20 unencrypted laptop computers at London Health Programmes, a medical research organisation based at the NHS North Central London health authority, could result in the biggest ever health care data breach suffered by the NHS.

According to a report in The Sun newspaper this week, the laptops went missing in May, and only three have been recovered. One missing machine, which was password-protected but not encrypted, contained details of 8.63 million people and the NHS medical records of 18 million hospital visits, operations and procedures. It has now been reported as stolen to the police.