Keene Communications, established in 1992, provides services including corporate comms, strategic marketing and public affairs.
Last year, Keene’s owner and former managing director Simon Quarendon stepped back to become chairman and promoted senior consultant Jake Rigg to succeed him.
The agency’s clients have included QAPSCO, the trade body for the UK's professional staffing industry, and identity authentication technology company TrustID, as well as the chemicals company DuPont.
AGO clients are from the transportation, freight, automotive, defence, security, engineering and technology sectors.
Adrian Graves has joined Keene as a senior consultant and will help the agency grow its UK, European and international portfolio, as well as support its existing business.
Quarendon said: "Clients rightly put a premium on working with agencies that can offer them both strength and depth and this is exactly what this new move is designed to give them. Adrian’s wealth of experience exactly complements our own."
Graves said: "This alliance has exactly the right strategic fit for both of us going forward – and makes a compelling business case for a whole range of reasons. It is the right time to move the AGO brand in another direction and our plans with Keene will provide important client benefits."