He succeeds Nick Houghton, who became CEO of the JMG Group, formed following a management buyout in 2020.
Fox is now responsible for the eight JM Glendinning businesses, based in Yorkshire, the North East, North West and the Midlands.
Fox said: “JM Glendinning is a progressive and ambitious business and I am very pleased to have this opportunity to move it further forwards in this phase of accelerated growth.
“As managing director of JM Glendinning, I will be working closely with the leaders of our eight businesses to support their aspirations through organic and acquisitive growth and quality recruitment, to ensure we achieve our target of doubling our premium income from £50m to £100m over the next five years.”
Houghton added: “Jake is an exceptional business leader and the natural choice to become MD of the JM Glendinning business. He built up Professional Risks from a standing start to what is now the most successful division in our group.
“I have always said that the success of this business is down to finding brilliant people and building businesses around them and Jake is the perfect case in point. Anyone who has ever met Jake will agree that he is the consummate professional who is an absolute pleasure to work with.”