DLA Piper, Skadden Arps Slate Meagher & Flom and Freshfields Bruckhaus Deringer top the deal adviser rankings for 2015 as global deal values saw a second consecutive year of growth to reach $4.3trn.

DLA and Skadden top the global tables by volume and value respectively, holding their positions from 2014, research from Legal Week's exclusive data provider Mergermarket has revealed.

Freshfields meanwhile topped the rankings for UK deal value in 2015, retaining its position held in 2014. It acted on deals with a total value of $361bn (£246bn), also placing it second by volume.

Piers Prichard Jones, head of the firm's London corporate practice says: "It takes time to build strong relationships with clients who will at some stage undertake transformational M&A. You have to invest many years in advance. Freshfields made decisions a few years ago to invest talent in building these relationships and securing our team top clients."

Continental coverage
In Europe DLA also put in a strong performance, where it led the way by volume advising on 243 deals worth a combined $27.6bn, while it also sat in first place in the UK by volume with 109 deals worth $7.1bn. Other firms to perform well in Europe include CMS and Allen & Overy which were second the third placed respectively.

Bob Bishop, head of corporate at DLA says: "If you offer clients advice that is relevant and commercial, delivered on time and to budget, they'll come back time and time again."

In addition to leading the global tables by value, Skadden became the first firm to work on $1trn worth of deals in a year taking roles on 298 deals valued at a combined $1.1trn.

Scott Simpson, Skadden's co-head of global transactions comments: "The 2015 M&A wave was driven by cross border strategic combinations (with a number of transatlantic deals representing a significant part of deal activity). Based on what we see thus far I believe that the cross border M&A market will stay active well into the new year."

The year of the mega-merger
A spate of mega mergers contributed to the annual growth in deal value in 2015, with November seeing the two biggest deals of 2015 announced, when Pfizer purchased Allergan and Anheuser-Busch (AB) InBev bought SABMiller.

The $160bn mega-merger between global pharmaceutical giants Pfizer and Allergan resulted in work for a raft of firms, including Irish heavyweight Arthur Cox, which featured in the European top 20 for deal value as a result of its role advising Dublin-headquartered Allergan.

AB Inbev, the world's largest brewer, announced in the same month that it would purchase its rival SABMiller for $120bn (£82bn). Freshfields advised AB InBev with a team comprising London M&A partner Mark Rawlinson, London head of corporate Simon Marchant and antitrust partner John Davies.

The biggest issue affecting deals is CEO's confidence

Bishop says that the deal will "stoke the beer industry, both in terms of forced sales to secure competition clearances and as a result of other industry players making moves to compete with the new drinks behemoth."

Looking forward to the pipeline of deals this year, Prichard Jones believes companies will take more into consideration before announcing large deals as a result of financial implications. He says: "Before Christmas, confidence was high. If you look now at announced or rumoured deals, for the first time in a while we're seeing the bidder's share price falling as a result of announcements. CEOs will worry as a result of this."

Rick van Aerssen, co-head of the firm's global M&A group concurs. "The biggest issue affecting deals is CEO's confidence. With the stock market difficulties, concern increases and it becomes more expensive to do deals," he adds.