Activity levels dropped in five boroughs - Croydon, Enfield, Hounslow, Kingston upon Thames and Harrow, which has become the home of the couch potato in London with only 13.3per cent activity levels. None of the 33 local authorities recorded a significant increase but Kensington and Chelsea was the most active in London in a cluster of boroughs in the south-west of the capital which boast participation levels above the national average.