Often described as the bellwether for how the UK’s law firms will report finances for the year, US firms saw an overall average drop of around 12 per cent in London revenue in 2009.
White & Case, which held on to its spot as the top US firm by revenue, saw London fee income fall from $245.9m (£159.8m) to $197m (£128m) for the year, while Baker & McKenzie saw its numbers fall to $184.5m (£119.9m).
“International law firms with offices in London which have heavily relied on transactional practices had a difficult year in the aftermath of the Lehman Brothers crash,” said Baker & McKenzie London managing partner Gary Senior.
US firms have been particularly hit by the drop off and lack of M&A work, as well as a fall off of banking and capital markets work.
However, California based Latham & Watkins was the only firm in the top 10 to see an increase in revenue after numbers climbed marginally from $150m (£97.5m) to $151.1m (£98.4m).
London headcount at the top US law firms also fell on average by more than 10 lawyers, with White & Case dropping as many as 116 lawyers during the year.
Fluctuation of both UK and American currencies has affected US firms, as some report in sterling, while others report in US dollars.
Senior said: “Things have relatively improved as we have seen a return to the IPO and M&A markets and there is a palpable sense of optimism.”