Detective Inspector Derek Grim is the head of the CID unit at Gasforth Police Station.
His attitude is that CID are superior to the uniformed Police and proclaims that the uniformed officers are "extinct...like the 'doo-doo' ". Grim harbours a poorly contained desire to be promoted, preferably away from unexciting Gasforth. Sometimes oblivious to subtleties, Grim is far more ignorant than he is willing to admit, which he regularly displays through his butchery of English phraseology (e.g. "You seem to forget, Kray, it's my arse on the line – so you'd better pull your finger out!") and his ill-conceived ideas.
He can be described as buffoonish and insecure about his own professional status and social standing. He has been married for 20 years to Tina (unseen) with whom he shares an intense love-hate relationship, as he often complains about their marriage, but he occasionally reveals that he does indeed love his wife. His son, Darren, was arrested by Goody in one episode. His rants (often against "fannying about", which he himself plainly does) are the source of numerous comedic lines. Despite his flaws, at least one episode reveals that Grim is fundamentally a good man, as he was greatly conflicted by D.C. Boyle's plan of planting evidence on the drug-dealer Harry the Spike.