"The police let him go."
Translation:Politiet lod ham gå.
lod is the past tense form of "at lade" whereas lad is the imperative form. At isn't required because verbs preceding "at lade" just don't take the at (the same as in English where the "to" isn't requite after "to let")
Got it! My confusion came about "let" is the English word for both of these forms and so the hint gave me the wrong word. I understand now. Tak!