Lord Chadlington, otherwise known as Peter Gummer, took over as CEO of Huntsworth last year after shareholders ousted the existing board in a coup aimed at turning the company around.
Chadlington joined forces with two other major Huntsworth shareholders -- former Halifax chairman Jon Foulds and former Warburg director Anthony Brooke -- to secure a £13m war chest.
In May this year, the company made three small acquisitions as part of its strategy to rebuild the Huntsworth network into a major PR group.
This is the company's largest deal so far. Harrison Cowley is number 25 in the PR Week's list of the top 150 PR agencies. Its clients include Marks & Spencer, The National Lottery, Land Rover and the Royal Bank of Scotland.
The company emerged from a management buyout from Saatchi & Saatchi in 1994 and, since then, revenue has grown by almost 20% each year. Last year, it reported revenues of £6.7m.
Huntsworth's clients include Heinz, Unilever, Levi Strauss, Whitbread and GlaxoSmithKline, and it had revenues of £11.4m for the 15 months to December 2000.
Under the deal, Harrison Cowley will retain its brand identity, existing management team and operating culture within the Huntsworth Group, the company said in a statement.