Abstract. London's development pattern graphically illustrates the importance and problems of urban definition. The pattern we observe is radically different depending on whether one examines the data for administrative definitions of London or London defined on functional boundaries. Even the answer to such an apparently simple question as to whether London was growing or declining varies according to the definition of London taken; the ambiguity as to whether London was decentralising, re-centralising or declining is equally striking. Even functional definitions of London and EU cities produce different pictures of the relative patterns of development, depending on whether those functional boundaries are fixed to reflect spatial patterns of employment and commuting at a given date or are updated lo current patterns. For reasons we can identify, this makes much more difference to results in some cities than it does in others. Updating the functional boundaries of London, for example, makes much more difference to ils measured size than is the case with Paris. London and Londoners are historically adapted lo long dislance commuting and strongly contrasting patterns of residential segregation compared to Continental European cities (especially Paris).These have been re-inforced by land use planning which generates a strong force for London's growth to leapfrog across the South East of England spawning satellite centres as it goes. Despite these measurement problems. however, the evidence allows one to conclude that there has been a sharp change in trends in London both absolutely and relative to other major EU cities. Recently population has been growing and recentralising and London's economic Performance improving.