Ecologist activist Mark 'Stone' has been an undercover police officer from 2000 to at least the end of 2009. We are unsure whether he is still a serving police officer or not. His real name is Mark Kennedy. Investigations into this identity revealed evidence that he has been a police officer, and a face-to-face confession has confirmed this. Mark claims that he left the police force in late 2009, and that before becoming an undercover officer he was a Metropolitan police constable.