Cater has been placed on gardening leave for three months after handing in his notice last week.
A former CEO of GCI Group, he was made regional director last year, when GCI Group was merged with C&W. He reported to C&W's global CEO Donna Imperato, based in New York.
Imperato said: 'Mark helped C&W build an affiliate network throughout EMEA. Now the region is established, that role is no longer necessary and Mark has decided to move on.'