Ropes & Gray, Withers, and Irwin Mitchell are the firms with the highest proportion of female partners, according to a International diversity survey that shows women make up on average one in four partners at top firms in the U.K.

Data from 51 of the largest firms found the trio topped the rankings for U.K. female partners overall, and also took three of the top four spots — along with Boies Schiller Flexner — when looking solely at equity partners.