PRWeek understands that Instinctif lost out to Brunswick in a competitive pitch one year ago but Inmarsat has now chosen to go with the former in what is thought to be a six-figure deal.
As well as taking the role of global corporate agency, Instinctif will lead on UK and European-based comms.
Instinctif’s team is headed by partner Jeremy Durrant and managing partners Damian Reece and David Simonson. They will report to Inmarsat’s external affairs and corporate comms team, headed by Chris McLaughlin, Jonathan Sinnatt and Katie Potts.
Inmarsat, which is listed on the London Stock Exchange, provides mobile satellite communications to the aviation and maritime industries, working with governments on both civil and military projects.
The team was widely praised for its work, and last November comms chief McLaughlin won the Mark Mellor Award for outstanding contribution to the PR industry at the PRCA Awards.
Plans for 2015 include launching a further two satellites to complete its Global Xpress network.
Tim Fallon, managing partner and CEO, capital markets and corporate affairs practice at Instinctif Partners, said: "As a business our scale and reputation are growing. Attracting global clients such as Inmarsat is testimony to our strength in depth and breadth as a business communications consultancy and our interconnected approach to reputation management."
Sinnatt, director of corporate comms at Inmarsat, said: "This is a very important appointment for Inmarsat, particularly in the year that we complete the worldwide rollout of Global Xpress, our $1.6bn (£1.06bn) superfast satellite broadband network. Instinctif will be a vital partner as we undertake the most ambitious communications programme in our history."