The offender walked into Fraser’s Budgens store and petrol station on the A44 at about 11pm and demanded money from members of staff while holding a revolver-style firearm.
A member of staff put the cash in a drawstring bag which the offender took and then left the scene on foot. No members of staff were hurt during the incident but they were extremely shaken.
Investigating officer, detective sergeant Oliver Jacques of Thames Valley CID, said: “We are releasing CCTV images in relation to the robbery and are appealing to the public to come forward with any information.
“If you saw or heard anything unusual in the area please contact police as soon as possible by calling 101 or visiting your nearest police station.
“If you do not feel comfortable speaking to police please contact the independent charity Crimestoppers anonymously on 0800 555111. No personal details are taken, information is not traced or recorded and you will not go to court.
“We are conducting a thorough investigation, including enquiries at the scene and reviewing CCTV. We are also trying to establish whether the firearm was real or an imitation.”