A man has been arrested on suspicion of robbery after a masked raider armed with hammer stole cash from William Hill bookmakers.
He remains in police custody where he is being questioned by officers.
A spokesman for the force said: "A 25-year-old man has been arrested in connection with a robbery at William Hill bookmakers in Sixth Street, Horden on Saturday evening.
"He is currently in custody and is being questioned by officers."
A masked man entered the premises and threatened staff with a hammer, before making off with a quantity of cash.
A reward has been offered, by the Association of British Bookmakers (ABB), for information that successfully leads to a conviction.
Anyone with information is asked to contact Durham Police on 101.
Callers are asked to quote incident number 419 of Oct 6 or contact Crimestoppers on 0800 555111.