Midlands law firm Gateley Wareing is to merge with Scottish solicitors Henderson Boyd Jackson.
The two have signed heads of agreement to link up with effect from January 1.
The new firm will be called HBJ Gateley Wareing and will have 57 partners and over 200 fee earners with offices in Birmingham, Edinburgh, Leicester, Nottingham and Glasgow.
It will immediately move into the top 60 UK law firms with an anticipated fee income in excess of #29 million in its first full financial year.
Outlining the rationale for the merger, Gateley Wareing senior partner Mike Ward said: "This is a true merger which will enable us to offer a broader service and is genuinely client driven.
"Both firms have grown significantly in the last few years and increasingly work for large national corporations, banks and financial institutions who expect their lawyers to be able to service a wider range of their needs.
"The merger will allow HBJ Gateley Wareing to work with clients in both England and Scotland and underpins our strategy for growth."
It hopes the move will extend its appeal to larger corporates and institutions.
Both firms said they had found early on in their negotiations that there was a strong cultural fit and common ground on key practice areas.
The initial approach came from HBJ.
Mr Ward said: "HBJ was looking south of the border and it was suggested by an organisation that we have mutual contact with that they should be talking to us.
"We had a chat and realised we had an awful lot in common."
The deal has been six months in the making and Mr Ward hopes it will in particular help Gateley's banking practice. Both Royal Bank of Scotland and Bank of Scotland have their headquarters in Edinburgh and HBJ has the better contacts.
Malcolm McPherson, chairman of Henderson Boyd Jackson, among the top ten Scottish law firms, said: "We quickly found that Gateley Wareing shared a similar outlook and placed a tremendous value on its commitment to client service, teamwork and the professional development of its personnel.
"Everything that went into the make up of HBJ was reflected in Gateley Wareing's approach. Both firms have a clear strategic vision of their future which makes the merger both compelling and exciting."
He continued: "We have both already consulted with a number of major clients and the overwhelming response has been very positive. The merger allows us to extend our capability into a key commercial centre in England to provide a greater breadth of expertise in our core practice areas. Indeed, we have already identified considerable opportunity to refer cross border work."
HBJ Gateley Wareing represents financial institutions, major corporates and mid market companies across a broad range of industry sectors as well as private individuals.
The firm's core practice areas will include banking and finance, corporate and commercial, employment, construction, litigation and dispute resolution, commercial and residential real estate and private client services.
It will be led by a management board comprising three representatives from each firm including Mr Ward and Mr McPherson as senior partners.
Mr Ward does not see a problem with the structure, pointing out that Gateley has had a management board for five years.
"It has worked very well for us and I don't see why it would not work for the merged practice. I am not worried who has the good ideas - let's get them on the table and implement them."
Henderson Boyd Jackson has been a major player in the Scottish legal market for over 100 years. Originally established to handle work for wealthy landowners, and entrepreneurs, it is now one of Scotland's leading firms of commercial solicitors, with 29 partners and over 90 fee earners operating from offices in Edinburgh and Glasgow.
Gateley Wareing is one of the leading independent firms of solicitors in the Midlands and nationally is 96th in the Lawyer Top 100 UK law firms.
The firm has 30 partners and over 200 staff with offices in Birmingham, Leicester and Nottingham.
Mr Ward said there were no plans for further mergers at this stage, though any approaches would be considered.
"There is no grand design, but we would look at everything on its merits. You cannot force these things.
"It has to be client-driven. Does it raise our ability to deliver? Are we comfortable with the people we are talking to? If you can tick all the boxes then I would not rule anything out."