Boothby, 44, has been promoted to operations director and will now be responsible for the commercial and operational running of Vizeum. He takes charge of financial management and will now run the agency on a day-to-day basis.
Grant, who wishes to spend more time with her family, will continue to be the managing director of Vizeum, but she will now concentrate on leading senior-level client relationships and developing the agency's proposition with the agency's head of strategy, Matt Andrews.
Vizeum was born last year out of BBJ and is part of Aegis Media's second and newest media network. Grant will work at the agency Monday to Wednesday.
Boothby has been at the agency for nearly 20 years. He joined the Bass buying unit in 1985, which evolved into BBJ in 1989, and he is regarded as a safe pair of hands.
"Chris is very experienced and has a strong commercial background. He has been working with the metrics and budgets and has proved himself to be a strong number two," Grant said.
As Boothby is taking on a broader role within Vizeum, he is handing primary responsibility for negotiation to Matt Platts, who now takes the job title of investment director. Platts was recently offered the investment director job at Manning Gottlieb OMD but pulled out at the 11th hour.
Grant said it was coincidental that the restructure came up just as Platts was looking for a new job. "He is ready for more responsibility," she said.
Mark Craze, the chief executive of Aegis Media, UK and Ireland, said: "Chris and Matt have both made strong contributions to the success of Vizeum. I am delighted to be able to promote from within and give the great talent we have in Vizeum the opportunity to further develop the business and their careers."