Freshfields Bruckhaus Deringer has reinstated itself as AstraZeneca's main UK firm for big M&A deals, scooping a key role on the company's $15.6bn (£7.78bn) purchase of MedImmune. Freshfields held off a chasing pack of City heavyweights, including Herbert Smith and Linklaters, which all have links with AstraZeneca. There is intense competition for AstraZeneca's corporate work as the company embarks on an acquisitive strategy to beef up its drug pipeline. Freshfields missed out on AstraZeneca's £702m purchase of Cambridge Antibody Technology last year due to client conflicts. Linklaters corporate partner Mark Stamp picked up that mandate in Freshfields' absence. Mayer Brown Rowe & Maw is advising AstraZeneca on the antitrust aspects of the MedImmune deal, led by EU and competition partner Frances Murphy. Latham & Watkins represented Merrill Lynch, which is acting as financial adviser to AstraZeneca. Dewey Ballantine is advising MedImmune.