"When it comes to international growth we're not after scale for the sake of scale and we only want a merger if it helps with our strategy," says Berwin Leighton Paisner's relatively recently appointed managing partner, Lisa Mayhew, of the firm's much-talked about discussions with Miami's Greenberg Traurig.

As far as Mayhew is concerned the UK firm would only be looking at any kind of union if it fitted with the wider strategic priorities settled on after she replaced long-term leader Neville Eisenberg last May and before the firm started discussions with Greenberg in October.

The discussions are only at the due diligence stage but at first glance the synergies between the pair are readily apparent. Both are known for their real estate practices and BLP is also targeting international growth in another of Greenberg's core practices – litigation – as part of its new vision, which looks to 2020 and beyond.

But as many can testify from bitter experience, it will take more than practice fit to pull off the first significant transatlantic deal in years. The continuing profitability gap between US and UK firms has ensured such mergers remain few and far between. And for every Hogan Lovells or Norton Rose Fulbright there are plenty more Ashursts or Eversheds, attempting to catch the eye of someone across the pond.

[A merger] would have to be enhancing for the firm and our partners, just as our other initiatives and lateral hires must be

The bigger challenge will be cultural fit and allaying the fears of UK partners scared of bloodshed at the hands of the more profitable US firm or somehow bridging the profitability gap without it, since the pair are pushing for financial integration.

Mayhew is adamant that BLP would not sacrifice its culture for Greenberg. She stresses that the deal, "would have to be enhancing for the firm and our partners, just as our other initiatives and lateral hires must be".

Since Mayhew took up her post BLP has spent a considerable amount of time working out what the firm's future focus should be, interviewing hundreds of clients for insight as well as benchmarking against other firms.

According to Mayhew clients highlighted innovation as a key differentiator for BLP, given much imitated services like its LOD contract lawyer service and its Manchester legal services centre.

She adds: "Positioning ourselves ever more strongly as a game-changer firm, delivering exceptional personal service and commercial advantage to clients felt very natural."

The firm hopes to build this reputation around a more balanced practice mix than it has historically had, setting targets to grow internationally in litigation and corporate risk; strengthen its corporate and finance capabilities; and of course capitalise on its real estate & infrastructure practice. This last is both a key practice and a sector for BLP under its new strategy, alongside the financial services, energy and natural resources and private wealth industries.

Everything has to be checked against all strands of the strategy

Mayhew says of the strategy: "Phase one was about identifying our potential and energising people, the second phase was about creating a winning vision and strategy and the third part, which is happening now, is the rigorous implementation of that strategy.

"This means everything has to be checked against all strands of the strategy, for example when investment prospects go to BLP's Executive Committee partners have to say how they meet the strategic aims in order to secure investment."

Motivating partners to increase cross-selling is also part of the strategy.

"We want to achieve more cross-selling across the business. Everyone has to believe in the strategy. It's about motivating partners and creating the right environment and culture for them to perform in. We have flexibility in how we pay partners, so we can incentivise them around the strategy."

As part of this push the firm has drawn up a series of partner principles that set out to define what characterises a good partner. "Are you sharing knowledge?" asks Mayhew. "How do you work with people? All of this has been aligned with partner appraisals, pay and targets to help with implementation."

At a more personal level, some of Mayhew's hopes are around gender equality. She comments: "Now I am managing partner, at a time when there are very few female law firm leaders, of course I recognise the responsibility to inspire more women to get into these senior roles in the future. To demonstrate that it's possible and achievable. Before, people didn't want to promote the gender agenda – they were uncomfortable with highlighting their difference, but we are past that phase now and we have a responsibility to talk about it."

I recognise the responsibility to inspire more women to get into these senior roles in the future

For now though it's easy to imagine Mayhew's priorities may be elsewhere, though she is keen to stress that all of these plans existed before the Greenberg merger talks and will continue with or without it.

She concludes: "While of course all talk will be of the merger, let's not forget the new offices we have opened in the last 12 months, the lateral hires we have made, the LOD announcement etc. I joined BLP because it had good momentum. I decided to stand for managing partner because I wanted to contribute to that momentum. I am determined that we will keep that going in the interests of our clients and our people."

But while the strategy may well be the same with or without it, it seems fair to say a merger with Greenberg would significantly accelerate progress. Indeed on the international front it seems hard to see how the firm will achieve its goals without Greenberg or a similar deal.