Robertson joins the agency following a period freelancing for charities including the CGD Research Trust, which funds research into gene therapy. He is also a former deputy director of comms and public affairs at the Commonwealth Secretariat.
He has also previously worked as a journalist editing Diplomat magazine.
In his new role he will report into Monument MD Mat Fordy.
‘We'll be looking to him to bolster our political relations and lobbying divisions,' said Fordy of the appointment.
Robertson will be working on the agency's clients including law firm CMS and architecture firm RMJM.