"It'll be a bloodbath. They'll merge and then hack each other to pieces," says a partner at a firm that has been through a transformational merger, of news of the three-way talks between CMS UK, Olswang and Nabarro.

It may be an extreme view, but getting any merger through the door is tricky enough at the best of times, let alone with three firms involved, and that's before the really hard integration job gets underway.

The latest proposed combination has many in the market concerned that it could result in sizeable back office cuts, given the amount of duplication that it would create, particularly in London.

With all three firms having their headquarters in the City, it is the most obvious area of overlap. There are also three offices in Brussels and duplicate offices in Hong Kong, Madrid, Munich, Paris and Singapore.

As Legal Week revealed on Friday, the Paris and Munich arms of Olswang are already considering alternatives to becoming part of the proposed merged firm, which based on current numbers would be home to nearly 1,000 partners and have combined revenue of just shy of £1bn.

Elsewhere in the UK, Nabarro has offices in Manchester and Sheffield, CMS has an office in Bristol and across Scotland as a result of its merger with legacy Dundas & Wilson, while Olswang has a base in Thames Valley.

In 2014, CMS and Dundas & Wilson cut 60 support staff roles ahead of their merger, with 40 going at Dundas and 20 affected across CMS UK and its third-party support suppliers Integreon, Initial and Xerox.

One former Nabarro partner says: "Ever since the credit crunch people have been talking about the importance of consolidation. No doubt this move means potential cost savings, as it's likely to mean some back-office redundancies."

Another ex-Nabarro partner raises wider questions about the impact on Nabarro's Sheffield office, saying: "What will happen to Nabarro's Sheffield office? I don't know. They've tried to sell it as a low cost resource but Manchester and Leeds are the traditional locations for those."

CMS's unconventional structure also throws up unique considerations for the combination, according to some. The international CMS network, which it is assumed the merged firm will still sit within, operates as a European Economic Interest Grouping of member firms, including CMS UK, which comprises CMS Cameron McKenna, as well as 12 overseas offices across countries including Bulgaria, Brazil, China, Mexico and Russia.

Fieldfisher managing partner Michael Chissick says: "It's a huge challenge to integrate cultures, IT systems and people. CMS's structure for international offices is very different – and bringing onboard non-London offices will be a huge challenge for them, because it's more of a loose federation, whereas Olswang and Nabarro offices are more fully integrated. They will also face challenges around name, remuneration systems, property and finding a business plan for the new firm."

A former CMS partner also views the firm's structure as a potential handicap, saying: "The structure is terrible, in my opinion. There is a loss of agreements for referrals and no solid alignment of interest."

However, one source close to Olswang believes the additional market reach provided by the CMS network will outweigh any potential difficulties caused by the structure.

He says: "CMS provides the global network. What Olswang and Nabarro need is to get bigger quickly; but they can't grow organically when profits aren't rising and they aren't going to attract partners in big numbers with their performance over the last three years."

Another ex-CMS partner is positive about the potential union: "I think it would be a good thing.  If I was still a partner at CMS I would be voting for it. Olswang has obviously been going through a hard time but is still a good firm – I think they're all a really good fit for each other."

A Nabarro partner adds that they are "very positive" about the merger proposition, highlighting the "similar sector focuses" between the trio.

Joe Andrew, chairman of Dentons, is optimistic about the path ahead, should the firms opt to go ahead with the deal. He says: "The quality and completeness of the integration is not determined by the legal structure but by the intent, creativity and steadfastness of the parties involved. Partnerships can be integrated or not, corporations can be integrated or not, vereins can be integrated or not.  It is all about the creativity of the parties involved.

"In addition, having done two-way and three-way combinations, there are advantages to doing a three-way. It is not exponentially more complicated and makes it easier to find best practices, rather than making the conversation your way or my way of doing things."