Bulge bracket investment banks, which normally eschew smaller deals because of the lack of fees, have unexpectedly dominated the mid-market in the first quarter, according to data from Thomson Reuters.

Bank of America Merrill Lynch, Deutsche Bank, Goldman Sachs and JP Morgan all jumped up the league tables for work on deals with a total value of up to $500m. Meanwhile, mid-market specialists such as PwC, Deloitte and KPMG lost market share.