Latham & Watkins and Cleary Gottlieb Steen & Hamilton have scored the prize mandates on one of the biggest pharmaceutical deals of the year, as Actavis has agreed to buy Botox-maker Allergan for $66bn (£42bn) in cash and shares.

The sale is expected to close in the second quarter of 2015, creating one of the world’s 10 biggest pharmaceutical companies with annual revenues close to $23bn (£14.7bn).