This is the sixth acquisition since 2012 for the legal services group, which is headquartered in Sheffield.
The deal adds two offices in Kensington and Mayfair to Irwin Mitchell’s existing base in London.
By acquiring Berkeley, which specialises in offering wealth advice to high-net-worth individuals, Irwin Mitchell plans to expand its range of services for clients with complex financial affairs in the UK and abroad. Berkeley offers advice in connection with international estate planning, trust advice, taxation, asset protection and probate and estate administration.
Andrew Tucker, chief executive of Irwin Mitchell said: “Berkeley Law has a very strong reputation in the marketplace and shares our focus on providing market-leading client care and innovative services.
“This is a deal which works for both businesses and the Berkeley Law team will be an excellent addition to our existing team, expanding still further the unique diversity and quality of the specialist services we offer to both private and business clients.”
Berkeley Law, and its subsidiary Berkeley Hurrell, which specialises in residential property and conveyancing, will both keep their names and continue to trade from the offices in Kensington and Mayfair.
The directors at the Mayfair-based law firm, Nick Rucker, Alex Ruffel and Tim Thornton Jones will become partners in Irwin Mitchell as part of this transaction.
Mr Rucker said: “We have been approached by many other suitors but Irwin Mitchell was by far and away the most creative, entrepreneurial and innovative business we have talked to.
“Irwin Mitchell understands better than any other how the legal industry in the UK is changing and crucially also has expertise managing and running complementary businesses that are not law firms.”
In recent years, Irwin Mitchell has grown by acquisition.
In November 2013, Irwin Mitchell acquired Manchester-based personal injury specialists MPH Solicitors. In March it bought the debt legal services firm HL Interactive, which is also based in Manchester.