Cook said it was “working closely” with the store team to support make sure “everyone feels supported”. Officers from Cheshire Police are appealing for witnesses.
The force said an unknown man entered the Church Street branch at about 10.10am on Sunday (February 10) and demanded the manager shut the store.
He then forced the manager to take him into the back office where he stole a quantity of cash from the tills, including euros and dollars.
The man fled on foot down an alleyway before running along the rear of the parade past Churchill Mansions and onto Mersey Street.
He is described as a white male aged between 30 and 40, approximately 6ft 2in tall of medium build with dark stubble.
The suspect was wearing dark sunglasses, a waist length parka-style coat with fur around the hood and blue jeans. He had a slight Liverpool accent and was carrying a red carrier bag.
Detective constable Daryl Gavin said: “The staff at this store have been left extremely shaken as a result of their ordeal and we are committed to doing all that we can to trace the person responsible.
"The investigation is ongoing and we are following a number of lines of enquiry.”
Kathryn Darbandi, Cook director of retail and customer experience, added: “The safety of our employees and customers is our absolute priority.
"We are working closely with our team in Runcorn to ensure everyone feels supported.”
Anyone with information or dashcam footage is asked to call Cheshire Police on 101 quoting reference IML 318198, report any information or submit footage via the Cheshire Police website, or call Crimestoppers charity anonymously on 0800 555 111.
