SJ Berwin has sealed its merger with Asia-Pacific giant King & Wood Mallesons (KWM), creating a $1bn (£657m) firm, with the SJ Berwin name set to disappear after a transitional period.

The tie-up, which marks the first major merger between a UK and an pan-Asia-Pacific firm, will go live from November this year after partner voting closed today (31 July).

The deal will combine KWM's 21 Asia-Pacific offices with SJ Berwin's UK, European and Middle East practice, creating a law firm that is among the top 25 largest in the world.

The combined entity will operate under the KWM banner, with the firm initially practising under the name King & Wood Mallesons SJ Berwin for a transitional period across the UK, continental Europe and the Middle East.

Under the terms of the tie up, SJ Berwin will join KWM's Swiss Verein structure, which currently includes three financially independent partnerships in China, Hong Kong and Australia.

KWM chairman Wang Junfeng and global managing partner Stuart Fuller will continue in their roles, with SJ Berwin senior partner Stephen Kon taking up the role of co-deputy chairman alongside Stephen Minns, who is currently KWM Australia chairman. SJ Berwin managing partner Rob Day will join the combined firm's executive committee.

The new firm will have more than 2,700 lawyers, including 553 partners. SJ Berwin will move into KWM's offices in Hong Kong and Shanghai, while London-based KWM lawyers will relocate to SJ Berwin's Queen Street Place headquarters.

Wang said: "There are significant synergies between our firms. We share the same values, goals, client focus and entrepreneurial drive. King & Wood Mallesons has always been a pioneer in Asia and the combination with SJ Berwin cements our position as the global law firm for the future."

Kon added: "Throughout its history, SJ Berwin has prided itself on being innovative. It has been prepared to be bold and challenge the market. This combination was the logical next step for the network. It positions our clients, partners and people to engage fully with the Asian Century, representing an opportunity for us to build a law firm for the future which is worthy of all we have achieved at SJ Berwin with our clients to date."

For the 2012-13 financial year SJ Berwin reported revenues of £184.6m, up 2.5% on the previous year, while profits per equity partner fell 11% from £635,00 to £565,000 this year.

SJ Berwin kicked of talks with the Sino-Australian firm last year, with the UK firm targeting a greater Asian presence beyond its existing offices in Shanghai and Hong Kong.

The top 20 firm has held a number of failed merger talks in recent years after a strategy to target the US market failed to come to fruition. Discussions with Orrick Herrington & Sutcliffe were called off in May 2010, with talks with Proskauer Rose also put on ice later that year.

KWM was formed via a merger between China's King & Wood and Australia's Mallesons Stephen Jaques in March 2012. Earlier this year, KWM also held discussions with Singapore's Wong Partnership about a tie up, but these ended when Wong Partnership opted to remain independent.

The tie-up in numbers:

- 553 partners (234 Asia, 163 Europe and the Middle East, 154 Australia, 2 US), of which 165 from legacy SJ Berwin - 2,233 lawyers (1,157 Asia, 731 Australia, 343 Europe and the Middle East, 2 US), of which 346 are from legacy SJ Berwin - 30 locations (11 China, 9 Europe, 5 Australia, 1 Middle East , 2 US, 1 Hong Kong, 1 Japan) - Circa $1bn (£657m) revenue

Market reaction to the combination:

"I think it is a good thing for King & Wood Mallesons to merge with a UK firm. It will strengthen its international coverage. The world is getting so small, whatever law firms do really needs be international. KWM has been the most successful of all the Chinese law firms in branching out.

"An acquisition or merger may not initially bring profitability up, however it is a very strategic and important move for long term survival because the legal field has changed for good.

"There are local law firms in China who are doing well, however, in the long term China will not be any different from any other international market. Companies from all over the world compete. If you're only local your representation will be limited. So in the long term I think a global view is very important." Xiang Wang, managing partner for Asia Pacific, Orrick Herrington & Sutcliffe

"I think this merger is a good thing. The firm has been searching for direction for a while and the question should be what if it hadn't gone through? They wouldn't have been in a good place and it wouldn't have looked good to have had another failed set of merger talks after what happened with Proskauer Rose.

"Senior figures at the firm are keen on the US so this was probably more of an opportunistic move on their part. SJ Berwin is a dynamic firm which reacts quickly, so once the approach was made they would have decided it was the right thing to focus on. However, this will be seen as a precursor to stage two, the American piece, so I wouldn't be surprised if something happened in the next couple of years.

"The Verein structure will have appealed to SJ Berwin partners as it maintains a sense of independence and culture. It is now part of a bigger organisation, a bigger firm, with a global reach. This brings the firm to the next level – it had pushed on quickly since 1982 and I'm sure this merger will help the firm push on again." Ex-SJ Berwin partner

"You can achieve [a global footprint] without necessarily doing a merger. For us we can do work in other countries, but we're not duty bound to go to a correspondent firm in that jurisdiction." Darryl McDonough, chief executive partner, Clayton Utz

"For KWM to merge with SJ Berwin is not that surprising. When King & Wood first merged with Mallesons, in the PRC market most people didn't expect that to be the last step of their global plan.

"I think it would be very difficult to imagine a merger between someone like KWM, which is unique in the market, and a magic circle firm. That would be very difficult to achieve." China-based partner at an international law firm

"They seem strange bedfellows. You've got a top Australian firm and a well-regarded Chinese firm, merging with a firm which I don't think even makes it into the silver circle. They are obviously looking for UK law capability and to have a semi-global footprint. But if you are a top tier firm in your jurisdiction, you need to merge with a top tier firm in another jurisdiction.

"In some cases you might merge with a smaller firm that has a particular type of client base you want to take on. But SJ Berwin is a full service firm that has been on the maket for a long period of time, so you've got to ask whether it's a move up, down or sideways. It has all the hallmarks of being a move downwards." Partner at a rival firm