Staff who had started the night shift at 11pm were instructed by police to shut the doors and stay away from the windows at around 2am and were not free to leave the building until the following evening.
Tates managing director Geoff Hallam praised the professionalism of his staff.
He told Convenience Store: "The incident happened at about 2am and the staff were told to close all the doors and stay away from the windows. From the start of their shift they remained stuck in the store for around 20 hours.
"All the staff acted professionally and co-operated with the police. We obviously lost the best part of a day's trading and I've not heard that we will receive any compensation. I expect the losses will have to come out of our insurance."