Trivia: There is an additional scene about two minutes into the end credits.
Trivia: Eggsy needs the code for the prison door that holds Princess Tilde. The code given is "2625." This spells out the word "anal" on a telephone keypad.
Trivia: Colin Firth did 80 per cent of his own stunts in this film.
Trivia: When Harry Hart is showing Eggsy the weapons of the Kingsmen, and shows Eggsy the knives in the shoes, Harry Hart says, "They used to have a phone in them, in the old days." This is a reference to the Get Smart TV show.
Answer: Details aren't given, but it seems that Dean is involved in local crime along with the gang that hangs around with him. Even if Harry is bluffing, and doesn't have specific proof, it is clear that he is abusive and he has the recording of him threatening Eggsy.