The male offender entered News Box on West Bars, Chesterfield, at 3.30pm yesterday (Monday) carrying a black handled three-inch blade.

He demanded money from the female shop assistant and made her open the til. The robber stole cash and made off towards the bus station.

A police spokesman said it was a surprising incident and added: "In broad daylight somone has gone into and robbed a shop in the town centre. Hopefully there would be more witnesses around at this time and we would ask people if they were in the West Bars area to jog their memories and think if they saw a man fitting this description either going in or coming out of the shop."

The offender is described as white, about 60 years old, six foot tall, of slim build with grey hair. He wore jeans and a brown fawn bomber jacket.

Anyone with information should contact Derbyshire Police on 0845 123 3333 or Crimestoppers on 0800 555 111.