The pair decided to launch The Joined-Up Training Company after working together at the Account Planning Group, where Grimes was the chairman.
"At the APG, Julian and I got involved with media-neutral planning about two years ago," Grimes said. "We realised that while there is a lot of theory on it in agencies, the real problem lies with clients managing the process. Our programme will help clients to lead complicated communications programmes with multiple channels and agencies."
The company offers two- or three-day courses and a series of modules on topics including channel planning, insight, creative and leadership.
The pair have included the theory and practices in a book, The Communications Challenge, launching next week.
The move means Grimes will no longer work with Barrett Cernis, where she has held a part-time head of planning role since September 2002. The agency is seeking a full-time replacement.
Separately, Grimes has joined glue London in a part-time capacity as an associate director to accelerate the development of its planning offering.