Slaughter and May has seconded City corporate partner Mark Horton to the government's Brexit unit, amid an increasing focus on the trade law capabilities of the UK's top firms.

Horton, the magic circle firm's relationship partner for the Crown Commercial Service, has been a partner at the firm since 1988. He will work with the government on its international trade negotiations in the run-up to the UK's exit from the EU.

The news comes as the UK's top law firms move to boost their trade law capabilities, amid growing client demand in the wake of last summer's Brexit vote.

This month, Linklaters signed up Cambridge University international law expert Lorand Bartels as a part-time senior counsel. In December, Kings College reader in international economic law Federico Ortino joined Clifford Chance (CC) on a part-time basis while the same month, senior European Commission lawyer Eric White joined Herbert Smith Freehills as a consultant.

Last September, Freshfields Bruckhaus Deringer recruited former HM Treasury lawyer Anthony Parry as a full-time consultant.

All four are specialists in international trade, EU and World Trade Organisation law.

Linklaters has also launched a standalone trade practice based across London and Brussels. The firm has appointed UK competition head Nicole Kar (pictured) to lead the four-partner practice alongside arbitration co-head Matthew Weiniger, City energy partner Charlotte Morgan and City litigation partner Greg Reid. Previously, trade fell under the firm's competition practice.

Weiniger commented: "In normal business you would turn to laterals, but there are no lateral partners – none. We are getting our associates to brush up on trade skills. Part of it is the question of what Brexit means for clients, but that will lead on to a proper client offering in London."

The practice also includes two counsel – Bartels, who is a specialist adviser to the House of Commons select committee on international trade, and Brussels counsel Jan Wouters.

It is understood that Linklaters has also seconded two partners to the government's Department for Exiting the European Union, although the firm declined to comment on this.

'Demand has been exponential' 

Magic circle firms are currently fielding many questions from clients as the UK grapples with the uncertainties thrown up by last summer's Brexit vote.

CC trade co-head Jessica Gladstone – who is part of a six-partner cross-practice trade team at the firm – says: "Demand has been exponential since Brexit. We need in-depth trade expertise to supplement what we as practitioners are advising on."

Allen & Overy has a standalone global trade group staffed by 12 partners. City regulatory partner Matt Townsend, who co-leads the group in London, says: "Client interest in trade continues to grow post-Brexit. We are working with a number of clients to model their strategy based on a variety of trading scenarios."

Freshfields, meanwhile, has a trade department within its competition practice, which includes around 50 partners globally, while Slaughters has a cross-specialism trade department, which includes eight partners.

Magic circle firms have tended to focus on more profitable competition work since US law firms and specialist boutiques piled into Brussels after the launch of the EU single market in 1993, bringing rates for trade advice down.

"It is not that people haven't been aware of the opportunities for trade law, it is that we haven't been able to make it work cost effectively," comments one Freshfields partner. "There is now obviously a desire to look very carefully at it, but whether this leads to significant amounts of work I think is questionable."

A Slaughters partner adds: "If there's a hard Brexit, I think mainstream corporate lawyers should be able to deal with trade issues. They already deal with trading in parts of the world where the EU doesn't have any trading arrangements."

However, Linklaters' Kar argues there will be plenty for private practice lawyers to do. "Some of the really big multinationals like Nestle and Unilever have trade law capability in-house for supply chain compliance work. Where they typically turn to law firms for support is in the area of disputes or for very complex advisory work. The other role for private practitioners is supporting corporates on negotiations with government."

She adds: "In the past, we passed on work to smaller boutiques. Now we are doing that work – which encompasses WTO rules and trade sanctions – ourselves."