Four out of the top five legal advisers on European mergers and acquisitions (M&A) in the first quarter of 2003 were not in the top 10 at this stage last year, according to data provider Thomson Financial.

The dramatic shake-up shows how one or two big deals, such as Olivetti's $29bn (€27bn) offer for Telecom Italia, can push firms up or down the rankings when activity is low.