A terrified female betting shop assistant was threatened with a hammer and locked in a back room by a robber posing as an employee.

The attack on the grandmother happened shortly before the Ladbrokes shop in Brighton opened on Saturday morning.

The woman arrived for work at about 9am and was sorting out the till when she saw a man banging on the door.

He was wearing a dark paisley tie, like ones formerly worn by Ladbrokes workers and, believing him to be an employee, she opened the door.

He followed her into the shop in Islingword Road and produced a hammer. He threatened to hit her with it before locking her in a back room.

The robber made off with more than £4,000 and left the woman trapped.

The woman, who asked not to be named, said: "When I saw the hammer I started shaking. He had to push me into the back room because I could hardly move my legs. Then he locked the door.

"I didn't know how long I would be in there and I was frightened out of my life.

"I just kept thinking of my family. It all started flashing by. It was one of the most awful things that's ever happened to me."

The woman made her way to the back of the shop where there was an outdoor patio area. But her only escape would have been over a neighbour's roof or into a nearby ground floor garden - a sheer drop of about 10ft.

A neighbour heard the woman shouting for help and called police.

The woman was so traumatised by the attack, her doctor signed her off work for a week.

The attacker is described as white, 25, with a local accent and straight dark jaw-length hair.

He was about 6ft, slim and wore a black leather bomber jacket, blue shirt and dark tie with a white paisley pattern.

He carried a dark green kidney-shaped bag.

Anyone with information should contact Detective Constable Jason Foy on 0845 6070999 or call Crimestoppers anonymously on 0800 555111.