Magic circle outfit Allen & Overy has been rewarded for rapid worldwide expansion with a jump in income - but has warned there are difficult times ahead.

The firm, headquartered in London, today announced half-year turnover of £582m, up 11% on this time last year.

The results show an improvement on the 7% increase reported for the 2010/11 financial year and reflect a six-month period when new offices were opened in Washington, Casablanca and Jakarta.

These markets, along with Australia, France and Germany, have formed the basis for the strong performance.

Wim Dejonghe, managing partner, said: 'We have delivered a healthy performance in the first half of the year, however with the Eurozone sovereign debt crisis and the US credit rating downgrade, we expect the second half to be slow. Our strategy of expansion into emerging and high-growth markets is paying off and we will keep investing in them.

'The office opening in Casablanca makes us the first law firm of our kind to set up in Africa, broadening our reach in yet further markets.’

The firm now employs more than 5,000 staff, including around 500 partners, working in 39 offices worldwide - 11 of which have opened in the last three years.