UK labour productivity is significantly lower than that of many other similarly advanced economies and has been so for decades, with negative implications for UK living standards. To make matters worse, during the last ten years labour productivity growth has stalled in most industrialised countries, and particularly in the UK. This has led to a renewed policy focus on productivity growth, as evidenced by successive government productivity plans and efforts to re-invigorate industrial strategy. This paper reviews the evidence on UK productivity performance, identifying what we know about the causes of its weakness, what we do not know and what this means for policy. We review the evidence through the lens of developments in economic measurement, drawing in particular on the work of National Institute colleagues past and present, and with a view to the key measurement challenges ahead that, unlocked, will help us understand better what is holding back UK productivity.