This Festschrift, dedicated to Cliff Jones, contains papers written by many of his closest collaborators. Cliff has an exceptional international standing for his groundbreaking research and leadership within the practice of formal methods, his career encompasses significant contributions to academia, industry, policy, and service. Cliff is a Fellow of the Royal Academy of Engineering, ACM, BCS, and IET, and in 2015 he was the inaugural Fellow of the Formal Methods Europe association. His career has included industry research in the UK, Austria and Belgium, a PhD at the University of Oxford, and academic and research roles at the University of Cambridge and the University of Manchester, and since 1999 at Newcastle University. Throughout his career, he has championed the essential role of formalism in design processes. His collaboration at IBM in the 1970s led to the creation of the Vienna Development Method (VDM), a seminal contribution that has influenced both practical industry applications and theoretical advancements. Cliff was the founding editor of the ACM journal Formal Aspects of Computing, a founder of the Formal Methods symposium, and he played a pivotal role in the IFIP Working Groups on Programming Methodology and Verified Software. His policy advocacy has been instrumental in fostering public discourse on the reliability of computing systems. The 30 contributions in this volume are a snapshot of the many current scientific developments inspired by or built upon Cliff’s contributions.