Andy Whittaker explores how an undercover police officer infiltrated a group of climate activists in Nottingham.

Eleanor Fairbraida and Ronny, discuss the first time they met Mark Kennedy aka 'Mark Stone'. Also former undercover officer Neil Woods, lifts the lid on the secrets of his old job.

Andy also hears from volunteers Pat Smith and Katie and ‘Lisa’, who went on to have a long term sexual relationship with Mark without ever knowing who he really was.

Mark's deployment still leaves many unanswered questions, which a judge-led public inquiry is trying to solve.