A masked man walked into Hemingford Service Station, in London Road, at about 10.30pm on July 9 brandishing a screwdriver. He demanded the member of staff open the till then leaned over the counter and grabbed the cash before making off. The offender is described as white, 5ft 7in, medium build and wearing a black Adidas top, dark trousers and white trainers. He also wore black leather gloves. Detective Constable Liz Cooper, investigating, said: This was a terrifying ordeal for the member of staff who feared she was going to be attacked. I would urge anyone who recognises the offenders clothing, or has any information, to call police. Anyone with any information should call DC Cooper on 101 or Crimestoppers, anonymously, on 0800 555111.