Despite the year-on-year rise being weaker than last August, when sales were ahead 9.8 per cent on the previous year, London sales remained much higher than the 1 per cent decline in total UK sales.
Heavy rain and a strong euro helped drive shoppers to stores and footfall was up 7.8 per cent in central London.
Heavy discounts meant clothing and footwear sales in the capital were given a boost, but sales of big-ticket items and homewares remained tough.
BRC director-general Stephen Robertson said: “For many, miserable August weather and high fuel costs made indoor London shopping more attractive than outdoor leisure or trips further afield. Heavy discounting, tourist spending and Londoners’ greater resilience to the slowdown also kept sales growing.”