Set up in 2014 by former Sir Lynton Crosby associate Peter Lyburn, the agency came to prominence in 2016 due to its third runway-focused work with Heathrow Airport, and its appointment of Caroline Preston, latterly David Cameron's head of broadcast.
Six hires so far this year, and a further three joining this month, bring the agency's consultant count to more than 25.
The most high profile is former Bell Pottinger partner Liz Morley. Also formerly of Maitland, she became the firm's fourth director on arrival at the start of the year, bringing with her new client Aggreko. Stonehaven will advise the power generation firm on financial comms.
The firm's other major new client win this year is Airbnb; Stonehaven replaces Pagefield on a policy and public affairs brief. The accommodation platform had worked with Pagefield since at least 2015.
Among others hires is Teneo Blue Rubicon's Matt Horrocks, formerly a pollster with Labour's 2015 election consultants Greenberg Quinlan Rosner, who has joined as head of research and insight. Laura Gabb joins this month from Burson-Marsteller as head of digital, while designer Nathalie Guinamard joins as head of creative output.
In addition, James English of public affairs firm Gplus Europe arrives this month as senior account manager. More junior recruits are new account executives Emilie O'Herne, Gemma Welch, Angus Boobbyer, and Andrada Dobre, who joins this month.
Two other clients were secured last year - a corporate reputation brief with energy firm Drax, which had no incumbent; and ScottishPower. The latter already used Stonehaven for customer strategy, and has now given it a corporate and public affairs brief. Portland had stepped away from that account when it took on a major brief from EDF last year.