Olsen will remain at the Engine Group-owned financial PR firm and will focus more fully on client and new business development.
Jaques has been a partner at Hogarth since joining in 2000 from investment bank Credit Suisse First Boston where he was V-P of its UK equity capital markets division.
He joined Hogarth following a 12-year career in investment banking, also working at HSBC and BZW.
Jaques will work closely alongside Chris Matthews, Hogarth's chairman. The move marks the first time a founding parter of Hogarth has not been leading the firm.
Olsen said: ‘I've enjoyed the role enormously but now is the right time - for me and for the business - for Andrew to take on the role. He has been a key part of Hogarth's growth to date and is exactly the right person to take the business forward. For my part, I'll be reverting to the aspects of this business that I love the most - my client and new business development work.'