The results, released this week by data provider Thomson, will be a boon to both corporate teams, traditionally viewed as not as strong as their magic circle counterparts’.
But A&O and Clifford Chance have trounced both Linklaters and Freshfields Bruckhaus Deringer in the table, which ranks legal advisers on announced European M&A deals by value from 1 January to 1 August 2007.
A&O topped the table, advising on just less than $400bn (£196.2bn) worth of deals. Clifford Chance came second with $356bn (£174.6bn). US corporate stalwart Sullivan & Cromwell also beat Linklaters and Freshfields into the top three.
This time last year A&O was nowhere to be seen in the top five rankings. Since the beginning of the year, though, it has scored lead roles on headline deals, such as advising ABN Amro on its potential €65.4bn (£44.2bn) merger with Barclays and advising Nuon on its £16bn takeover by Essen.
Meanwhile, Clifford Chance's private equity team has particularly boosted its corporate rankings. It advised Kohlberg Kravis Roberts on the £11.1bn buyout of Alliance Boots earlier this year. The corporate group is also advising Barclays along with Sullivan on ABN.
Linklaters, which topped the table this time last year, still advised on $306bn (£150.1bn) worth of deals, 14 per cent more than last year, but this only secured it fourth place. Freshfields trailed in fifth with $263bn (£129bn).
But Linklaters and Freshfields scored lead roles in July's biggest announced deal, Rio Tinto's $34bn (£16.75bn) bid for Canadian aluminium company Alcan.
Taken in aggregate, according to Thomson there have been $1.6tr (£785bn) worth of deals in Europe since January, up by a massive 84 per cent on this time last year.