At around 9.30pm yesterday (Tuesday 24th March) two men entered the convenience store, within which the post office is located in Ropery Road, wearing dark clothes and balaclavas and holding hammers.
They demanded money from the female cashier then reached over the counter and took money before running out of the shop.
Nobody was hurt in the incident but the cashier was left shaken up.
Police would like to hear from anyone who may have witnessed anything in connection with the robbery or anyone who thinks they may have any information that is relevant to the enquiry.
Please contact Lincs Police on the non-emergency number 101 quoting incident 400 of 24th March, alternatively contact the independent charity Crimestoppers anonymously on 0800 555 111.