Martin is Declassified UK's chief investigator. He previously worked for The Guardian, Channel 4 News and openDemocracy, where he was UK Investigations Editor. His book, ‘Parliament Ltd’, exposed widespread corruption in British politics and sparked multiple inquiries by Westminster authorities. It was described as “ground-breaking” by the Sunday Times, while the New Statesman said the book was “a powerful reminder that reporters can serve the public good”. Martin has published investigations on issues ranging from lobbying and dark money, to espionage and human rights. He has also produced investigations for TV and YouTube, including going undercover. Between 2015 and 2016, he co-presented a live stage show with comedian Josie Long which combined investigative journalism with stand-up.