Despite substantial structural change and a significant intensification of competition in the UK financial services sector in recent years, the UK banking sector remains relatively under researched. This paper uses a panel data sample covering the main UK banks over the period 1984 to 1995 to investigate relative efficiencies within the sector and to analyse productivity change in UK banking over the sample period. The results provide important insights into the size-efficiency relationship in UK banking and offer a perspective on the evolving structure and competitive environment within which banks are currently operating.