From what I heard, the film is lacking focus as no environmental activist will engage with the filmmaker. Mark Stone was a police officer who duped his way into the environmental movement for 7 years. My contact tells me that Mark Stone has very little charisma on camera so is a bit dull to watch. Blue screen and re-enactments have been used to try and liven the film up.

This is from Channel 4 press office:
Directed by Bafta-winner Brian Hill and narrated by Kennedy, Cutting Edge also features interviews with the police to reconstruct the story of how Mark Kennedy went from being a regular south London police officer with a wife and two children, to becoming Mark Stone. This was Mark the environmental campaigner, militant activist and undercover cop who broke into power stations, learned how to make bombs, infiltrated groups hell bent on attacking major corporations and stood arm in arm with anti-capitalist anarchists. He also had a relationship with a female activist for four years and was even beaten up by fellow police officers unaware he was undercover and all the time he was feeding intelligence back to his handlers.

Now, with his cover blown only a few months ago, he lives in fear for his life. He is separated from his wife and family. The woman he fell deeply in love with as Mark Stone never wants to see him again. For the first time, Kennedy is returning to face up to himself, his actions and to the people who claim he betrayed them.