Following months of speculation, last week Slaughter and May confirmed the hire of former Serious Fraud Office (SFO) director David Green.

While the hire undoubtedly looks like a major coup for the firm, Green's remit at Slaughters will be restricted by the conditions placed on him, limiting the SFO-related work he can be involved in, and the SFO is set for a new broom under the leadership of his successor, Lisa Osofsky.

So what is Slaughters' thinking behind the hire? Partners around the City suggest the move is part of a play by the magic circle firm to align itself with its US white-collar contemporaries, while also meeting the expectations of an increasingly multinational client base.

Among America's elite law firms, having prosecutors within the ranks has long been a feature of white-collar practice. As investigations work has become increasingly globalised, UK firms have looked to follow suit, and Green is the latest in a string of former SFO figures moving into white-collar private practice in London in the decade since the financial crisis.

As the crisis erupted in 2008, Robert Wardle, another former SFO director, joined DLA Piper as a consultant, while in 2011 and 2012, SFO head of assurance Charlie Monteith and bribery and corruption head Satnam Tumani joined White & Case and Kirkland & Ellis respectively.

The revolving door continued to spin last year, with long-serving SFO prosecutor Sacha Harber-Kelly joining Gibson Dunn & Crutcher's London base and Freshfields Bruckhaus Deringer recruiting bribery co-head Ben Morgan, while the trend has not been confined to the SFO, with director of public prosecutions Alison Saunders set to join Linklaters this October.

Green's experience of the way prosecutors work and of their expectations of corporate clients will be invaluable to Slaughters

There are obvious harmonies between Green and Slaughters. One, a pedigree magic circle firm looking to grow its global investigations practice, which this year added to its ranks in Hong Kong with the firm's third ever lateral hire – Hong Kong Securities and Futures Commission enforcement director Wynne Mok. The other, an ex-SFO director who – before closing out his six-year tenure in April – saw the regulator out of a tumultuous period to foster a culture of transparency and cooperation, championing the use of deferred prosecution agreements (DPA).

Indeed, Slaughters acted for Rolls-Royce on the SFO's four-year investigation into bribery and corruption at the company, which culminated with a DPA agreed in January 2017, in one of the highlights of Green's tenure. This case, among others, has led some City partners to describe the magic circle firm's approach as "prosecutor-friendly", ushering clients through investigations by way of what one leading white-collar crime partner calls "extraordinary cooperation". The Rolls-Royce deal "is their playbook", another says, while a third partner suggests the approach was less about attack than mitigation and cooperation.

However, Slaughters partners are keen to push back against these claims, citing their work on matters such as the 2015 Olympus case, in which the SFO dropped its charges against the Japanese optics maker.

Slaughters co-head of global investigations Jonathan Cotton, who led on Olympus, says: "We always aim to deliver the best strategic and commercial result and have great experience in doing so for clients under investigation. The addition of Sir David, with years of criminal experience both prosecuting and defending, enhances and consolidates our ability to do that, in an area that is increasingly important to our clients."

Indeed, one City partner suggests the appointment was akin to bearing a 'kitemark', while a white-collar partner at a US firm in London agrees with the general sentiment that it is "a good hire" and "a good match".

Stephenson Harwood partner Tony Woodcock described it as "a feather in Slaughters' cap", and that Green had been part of "a marked step-up in the readiness of the SFO to take on difficult global investigations, to work in parallel with other overseas prosecuting agencies, and to embrace new ideas such as DPAs and strict liability corporate offences".

Woodcock adds: "His experience of the way prosecutors work and of their expectations of corporate clients will be invaluable to Slaughters."

However, given the restrictions placed on Green as a former Crown servant, some have questioned how influential he can be, given he is required to steer clear of any matters relating to investigations conducted by the SFO during his tenure as director, including ongoing probes Slaughters is acting on such as Ultra Electronics and British American Tobacco.

What is more, many expect Osofsky to usher in a regime quite unlike Green's – one characterised by greater speed and a different set of inducements for self-reporting.

Under Osofsky, there will be "a much faster regime" that will "encourage more companies to step forward", one City partner claims, while adding that he expects there will be "a better dialogue between companies and the SFO". Another suggests Green's ability to advise clients on an inside track could therefore become "historical".

There is a need to have an English prosecutor for the US market

The move also suggests Slaughters is keeping one eye on the US market. The firm often acts alongside elite US counterparts on its global investigations involving regulators on both sides of the Atlantic. Examples include working with Sullivan & Cromwell on Standard Chartered's $250bn money laundering scandal in 2012, co-counselling with Debevoise & Plimpton on Rolls-Royce, and partnering with Paul Weiss Rifkind Wharton & Garrison on Deutsche Bank's £2.1bn fine in 2015 for its part in the Libor scandal.

Skadden Arps Slate Meagher & Flom white-collar partner Elizabeth Robertson claims that by bringing in Green, Slaughters is targeting the American market: "There is a need to have an English prosecutor for the US market. Some English clients are less impressed about having a former regulator on the books. But this is a play for the US, where companies expect to see former prosecutors [in the firm]."

A partner at another US firm in London, who wanted to remain anonymous, says: "It's rare that elite white-collar practices in the US don't have at least two or three prosecutors – experienced ones – in the team. It's just standard practice and has been for a good while. Doing things any other way is almost unthinkable." 

In this rapidly growing market, with US competitors continuing to lay claim to the biggest deals the City has to offer, the UK's elite might find themselves having to rethink their long-term strategies in the white-collar world.

"British American Tobacco, Tesco, Rolls-Royce, Kodak and others – they tend to go to the magic circle, perhaps because they feel they can't be criticised for doing this," said a partner at a large US firm. "But we're starting to see disruption around that. Simmons & Simmons is an example, so are Skadden, Willkie Farr & Gallagher and WilmerHale. General counsel are being more thoughtful about who they instruct."