Sivell, who was previously associate creative director, will work with the existing creative director, Matt Powell. Both will be jointly responsible for creative output from the agency's London office.
Clark, who was formerly a lead creative, will be responsible for the day-to-day running of the department. The restructure comes as Profero realigns its creative departments in key global markets. It has recently appointed Pascal Hierholz, a former creative director of McCann Erickson in Canada, as the creative director of its Shanghai office.
Powell said: "Liz has shared with us a wealth of tech-nological insight and a passion for the industry."
Sivell said: "Matt and I have different qualities, which make this an exciting creative explosion."