US law firms took half of the lead roles on Europe's 10 biggest M&A deals in 2016, in a year in which the total value of UK M&A activity more than halved in the wake of the Brexit vote.

Europe's top 10 deals during 2016 – topped by Qualcomm's $46bn (£37bn) takeover of Netherlands tech company NXP Semiconductors (see full list below) – handed 11 lead roles to US firms, including two each for Simpson Thacher & Bartlett and Skadden Arps Slate Meagher & Flom.

Skadden led for NXP on the Qualcomm deal and also took the key role for 21st Century Fox on its takeover bid for Sky. Simpson Thacher, meanwhile, led for ChemChina on its $46bn (£37bn) bid for Swiss agribusiness Syngenta, and advised Tyco International on its $16.2bn (£13bn) merger with Johnson Controls.

Despite the dominant showing from US firms, Freshfields Bruckhaus Deringer and Linklaters picked up three and two lead roles on the top 10 deals respectively, including acting on opposite sides of the London Stock Exchange-Deutsche Boerse merger.

The findings, based on Legal Week research into Mergermarket's largest deals by value in Europe in 2016, follow a tumultuous year for UK M&A value after the UK voted to leave the European Union in June that year.

Mergermarket's data shows the total value of UK M&A activity more than halved from $415bn (£340bn) in 2015 to $188bn (£160bn), as total deal volume fell by 3.5% to 1,418.

Total European M&A value fell by more than 10% to $797bn (£656bn), although deal volume remained broadly stable, while total global M&A value dropped 18% to $3.24trn (£2.6trn), as volume fell 4% to 17,369.

The largest instruction for Freshfields was representing Japan's SoftBank on its £30.2bn (£24.3bn) bid to acquire UK smartphone chip designer ARM. The deal, which completed in September, was the third biggest deal in Europe last year. It was announced less than one month after the shock Brexit vote, with SoftBank spurred on by a plunge in the pound that followed the vote, making ARM a more attractive target.

As well as its role on the LSE-Deutsche Boerse merger, Linklaters also took a lead role on National Grid's sale of a 61% stake in its gas distribution network to an international consortium of investors.

Trump's strongly pro-business policies and appointments make the US a very attractive market for investment

Commenting on activity levels last year, Linklaters corporate partner Iain Fenn said overseas buyers dominated public transactions in the latter half of 2016. He added: "2016 was strong for us – not quite a game of two halves; a very busy first half, with a little bit of a hiatus through Brexit, then a pickup towards the back end of the year."

Overall, the top European adviser by value was Freshfields, which acted on 206 deals with a total value of $269.5bn (£215.9bn), with Allen & Overy, Linklaters and Clifford Chance placing 4th, 5th and 6th respectively, behind White & Case and Cravath Swaine & Moore in 2nd and 3rd.

By volume, DLA Piper retained first place with roles in 268 deals worth a total of $75bn (£60.1bn), followed by CMS, A&O and Linklaters.

Globally, White & Case topped the 2016 rankings by total deal value, advising on 319 deals worth a combined $665bn (£534bn), placing it ahead of Sullivan & Cromwell and Davis Polk & Wardwell, while DLA also topped the global rankings by volume, after advising on 473 deals during the year.

Outlook for 2017

Looking ahead, M&A partners are expecting the new US administration to be positive for the global market, with an expectation of 'big-ticket' foreign takeover deals in the UK due to the falls in sterling and a rise in European investment into the US.

Freshfields US corporate head and global M&A co-head Matthew Herman said: "We think the US M&A market will continue to be very robust, with the new administration likely to be more positive for M&A overall. We believe that the increase in activism in Europe will continue, and that will drive transactions, as will bullishness in the boardroom from the best placed corporates."

Fellow M&A co-head Bruce Embley said several European corporates have "a lot of cash and debt still readily available for the right deals".

Scott Simpson, co-head of the global transactions practice at Skadden Arps Slate Meagher & Flom, told Legal Week-affiliated publication Focus International last month that Brexit could lead to an increase in outbound M&A activity in 2017 from Europe, as corporations seek to increase their exposure in the US and other less volatile markets. "We're in a period where people are just trying to recalibrate," he said. "The uncertainty in Europe isn't going to go away for a while, whereas the US is likely to be a growth engine."

White & Case global M&A head John Reiss said: "Donald Trump's strongly pro-business policies and appointments make the US a very attractive market for investment, and we believe the perceived strength of the US will encourage increased confidence, leading to continuing heavy interest in complex, cross-border M&A on a global basis."

Fenn highlighted Chinese interest and South African interest in the UK. "As the pound is cheaper, a certain number of European clients have been also been looking at opportunities and we expect they will continue to do so," he said.

Despite some positive signs, Herman concluded that "much more work" needs to be done to avoid deals falling through. "Our optimism is tempered by the historically high levels of failed deals last year, emphasising the need for that much more work done upfront – either ahead of approach or prior to signing and announcement," he added.