This paper gives an overview of several important issues concerned with the measurement and understanding of long-term sea level change, which is one of the most important topics in sea level science. The issues discussed span science, technology and our ability to fund and operate the national and global observation networks required for a proper understanding of long-term change and its impacts. Many of these topics were explored at a 'Celebration of UK sea level science' at the Royal Society on 16-17 February 2004, and are discussed further in a number of papers in this volume.