As engines of growth and social integration, cities are the magnets for more than half the world's population. "Understanding Cities" is a five-part public debate addressing the complexities involved in designing and running the powerhouses of today's global economy. This series will address the most provocative ideas in city-making, including environmental responsibility and climate change, social cohesion and the built form of cities.

The debate about London's future centres on the ability of its transport system to handle millions of passengers daily. This event assesses how transport shapes and is shaped by the city's environmental pressures and its quality of life.

Peter Hendy is Commissioner of Transport for London and Tony Travers is Director of the Greater London Group at LSE.