Shadwell F.C. is actually based on Millwall F.C. Shadwell's nickname is The Dogs and their ground is called The Kennel. Millwall's nickname is The Lions and their ground is called The Den. West Ham's nickname is The Hammers.
Shadwell actually exists and can be reached on the London DLR network.
The plot of the film is loosely based on "Operation Full-Time", a Scotland Yard undercover operation which attempted to identify the leaders of West Ham United F.C.'s firm, the Inter City Firm (ICF). However, none of the real life officers suffered John's (Reece Dinsdale) fate in the film.
Lee Ross, Richard Graham & Perry Fenwick also appeared in the sequel, ID 2: Shadwell Army
Peter Blythe who plays DAC Evans and Richard Graham who plays Trevor both worked with Reece Dinsdale in Home to Roost