The Llyn Cerrig Bach assemblage is one of the most important collections of La Tene metalwork discovered in the British Isles. It came to light during construction work in 1942 at RAF Valley in north-west Anglesey, when it was disturbed during the extraction of peat from the Cors yr Ynys bog located on the southern margin of Llyn Cerrig Bach. A total of 181 iron and copper alloy artefacts are known to have been recovered from the airfield, of which all but four are now in the collection of the National Museums and Galleries of Wales. This book incorporates a catalogue and discussion of the copper alloy artefacts in this collection. In addition to a typological study of this internationally important collection of Iron Age metalwork, the volume includes discussions of metalwork and insular La Tene art chronology, fieldwork at the site and metallurgical analysis of the assemblage. In the concluding chapter, the site is evaluated in its British and wider context and a revised interpretation of the character and chronology of deposition is proposed, which sheds light upon both the character of Iron Age Anglesey and the Roman invasion of this part of Wales.