World Anti-Doping Agency (WADA) chief spokesperson Ben Nichols is due to stand down from his position in May.
Nichols, who has spent the last four years working in the Montreal-based WADA headquarters, is planning to return home to London.
He has overseen media relations during the most challenging time in the organisation's 17-year history since assuming the post in June 2013.
This has overlapped with the Presidential tenures of both John Fahey and current head Sir Craig Reedie.
He has played a key role during the unveiling of the Pound Report into Russian doping as well as the ongoing process to reform the global drugs testing system.
"After four hugely fulfilling years at WADA, I have decided to move on from my role and back to the UK in May to seek a new challenge in the world of sport," Nichols confirmed to insidethegames.
Nichols’ international career has spanned both Britain and United States as well as United Arab Emirates and Canada.
He has previously held other roles including as chief press officer of the Association of Tennis Professionals and Women's Tennis Association Dubai Tennis Championships.
He has also served as senior press officer for the Lotus Renault GP Formula One team.
No replacement appointment has yet been announced at WADA.