Two thirds of Slaughter and May's partners were educated at the Universities of Oxford or Cambridge and about half were privately educated, according to Legal Week research that lays bare the dominance of that background across the top echelons of the Magic Circle.

Across all five elite firms – Allen & Overy, Clifford Chance, Freshfields Bruckhaus Deringer, Linklaters and Slaughters – nearly 50% of the 804 London partners hailed from one of the two elite universities, based on data compiled from partners' website biographies, legal directories and LinkedIn profiles, as well as alma mater resources.

The data monitored attendance at Oxford or Cambridge, whether at undergraduate or postgraduate level.

Additionally, in every single Magic Circle firm, privately educated partners formed the largest group by educational background. In total, they accounted for more than half of the U.K.-taught total for which there is available data, according to the firms' own diversity statistics.

About 2% of the U.K.'s current university population attend Oxbridge while about 7% of the population attend private school.

The figures call into question the firms' hiring practices and have attracted criticism from campaigners such as Dr Wanda Wyporska, executive director at Equality Trust, who said "there is a huge amount of work to be done".

The Oxbridge connection

Slaughters' partnership was by far the most lopsided in terms of Oxbridge representation. Of its 92 partners, 31 went to Oxford while another 30 went to Cambridge, while just 28 went to any other university. Three partners had no available data. The firm declined to comment on the lack of diversity.

But Slaughters was far from alone. At both Freshfields and Linklaters, 48% of U.K. partners attended Oxbridge, the research found. At Clifford Chance and Allen & Overy, the figures were slightly lower, with four in 10 Clifford Chance partners attending Oxbridge, and 35% at A&O.

Oxbridge representation is nearly 50% overall.

The combined total puts Oxbridge clearly ahead of the next best-represented university, Bristol, which accounted for 39 partners (5%) across the five firms. The third and fourth best-represented universities were University College London and King's College London, with 26 (3%) and 25 (3%) respectively.

Just one university outside of England supplied more than 10 partners to the Magic Circle: Edinburgh. While fewer than five partners in total attended university in Wales or Northern Ireland.

Outside of the Russell group, representation is also extremely low. At Slaughters for example, just one partner attended a non-Russell Group U.K. University. Reading was the most-represented non-Russell Group university, amassing a total of five partners (less than 1% of the total) according to the Legal Week analysis.

Old school ties

When it comes to schooling, privately educated partners represented the largest educational group across all five firms, accounting for an average of 43% of all partners.

However, when viewed as a proportion of U.K.-educated students on which information was available, the stats were even more slanted.

Privately educated partners outnumbered state-educated partners by, on average, 10%. Allen & Overy has the most disproportionate ratio of 61:39, followed by Slaughters on 58:42.

A fifth of Linklaters partners did not declare their educational background, but its privately educated partners still outnumbered those who were state educated.