Howden paid 1.1 billion pounds ($1.5 billion) for the acquisition, according to a source familiar with the matter, its largest acquisition to date.
The deal will create a UK business at Howden managing over 6 billion pounds of gross written premiums for more than 1.7 million policyholders in Britain and Ireland, the firms said in a statement.
Aston Lark chief executive Peter Blanc will become executive chairman of Howden’s UK retail broking operations.
Aston Lark specialises in complex commercial and private client insurance and employee benefits advice.
Globally-focused firms such as Howden are competing for scale with the world’s top three insurance brokers Marsh, Aon and Willis Towers Watson. A $30 billion merger between Aon and Willis Towers Watson fell through in July.
Following the Aston Lark deal, “you’ll see us really expand our operations in Europe,” Howden Group CEO David Howden told Reuters, adding the firm was also “expanding rapidly” in the Asia-Pacific region.