Running with the Firm

I've mentioned the book in a couple of recent posts so better follow through. In 1987 James Bannon was a policeman assigned to work under-cover to infiltrate Millwall's hooligans. After the operation ended in 1989, he quit the force to become an actor (figuring he'd been getting paid to pretend to be someone else so why not keep doing it for more money and a lot less danger!) - he appeared in 11 men against 11 and, according to his bio on here, drop the dead donkey and a couple of other things. He also put his story in to a screenplay which was used for I.D. and eventually the book Running with the Firm.
When I first watched ID I suspected that a lot of the incidents were based on real stories, especially the part where they hide in a pharmacy and arm themselves with spray, as they just seemed too crazy to be made up (if that makes sense). My best guess though was that they compiled a load of anecdotes from hooligans of various clubs/areas. For the undercover operation to be real and for the police to have been involved in all of these incidents was beyond my reasoning.
Disclaimer - according to James Bannon's book, the stories were real