From 2014 to 2016, Seddon worked in the Communications and Speechwriting Unit for the Secretary-General of the United Nations, Ban Ki-moon. During this time he again lived in Manhattan, New York City. He subsequently became Director of Communications for the International Commission on Financing Global Education Opportunity, chaired by UN Special Envoy for Global Education and former UK Prime Minister, Gordon Brown. In September 2017 he became an Adjunct Professor in International Relations at Columbia University, New York, in the Harriman Institute. He returned to New York in August 2018, to work as Media Adviser to the President of the UN General Assembly, 73rd Session at UN Headquarters.