DETECTIVES have congratulated a shop assistant for her quick-thinking after a masked man demanded money from her at knifepoint.

Police are now appealing for witnesses to help trace the man who held up the newsagents in Darlington on Tuesday(25) night.

A man, wearing a balaclava over his face, entered the store before brandishing a knife and demanding money from a female member of staff behind the counter.

The incident took place at Mills general store, in Cleveland Terrace, at around 9.30pm on Tuesday.

The quick-thinking woman, who is in her 60s, told the robber she needed to get the keys from the office and before the knifeman could react she went inside and locked it, leaving him unable to gain access to the till.

The only other member of staff working was a male colleague, who was already in the office and there were no customers in the store at the time.

After the robber left the store, the pair came out of the office, unhurt but shaken.

The man police want to question is described as about 5ft 8ins tall and was wearing a dark hooded top along with the balaclava. It is thought he fled the area via Elton Road.

Police would like to speak to anyone who saw the man leaving the store or who saw any suspicious people or vehicles in the area.

DC Sarah Honeyman said: "I would say the ladys quick-thinking has saved the day.

"We find any incident involving a weapon concerning, as there is always an element of possibility that they might use it. Fortunately, this time no one was hurt. However, we are taking this very seriously," she added.

Police are asking anyone in the area at that time on Tuesday evening to contact them if they saw anything suspicious.

Anyone with information can call police on 0845-60-60-365 or Crimestoppers on 0800-555-111.