Adrian Knight, head of the investment banking group at Ashursts, is joining Shearmans' London office as its first English law M&A partner.
Knight's exit will bring the tally of Ashurst departees who have left to join Shearman & Sterling to five.
Last year Stephen Mostyn-Williams left Ashursts and was followed two months later by three other banking partners who joined the US firm's European acquisition finance department.
Knight refused to comment on his departure but it is understood he resigned from his position on 13 May.
Shearman & Sterling already had a relationship with Knight through referring English law M&A work to him for a number of years.
But Pamela Gibson, managing partner at Shearman & Sterling, refused to comment on whether the firm approached Knight about the job.
However, she says the constant recruitment of banking partners from Ashursts is “no more than a co-incidence”.
Geoffrey Green, senior partner at Ashursts, says: “Knight believes a US firm will be better suited to his personal goals. He has been part of a strong corporate team across Europe which will continue.”
He adds: “People come and people go.”
Knight will leave a 30-strong investment banking department to join a growing unit at Shearman & Sterling. Gibson says the firm will continue to recruit further staff in its M&A and capital markets department.
Green says Knight will be replaced by promoting a lawyer from within the firm.
One legal insider says: “You are not going to leave Ashursts to go anywhere else but a US firm.”
He adds: “Ashursts is a good firm, so when you leave you have to make a quantum leap into something different.”
Shearman & Sterling itself has recently been hit with the departure of its former managing partner William Lee.