The National Cyber Security Centre has recently updated the NCSC Problem Book on cyber-physical security. The book highlights significant challenges that require collaborative efforts across disciplines to secure systems that connect the physical and digital worlds. It emphasises the urgency of integrating modern security measures into operational technology and targets academics and individuals interested in cyber-physical research. The book outlines significant challenges for the next 5 to 10 years. It presents six specific problems, including building security for systems with long operational lives and integrating secure devices at the system level.