The retailer is attempting to break the Guinness World Records for the title at an event at Alexandra Palace on 1 July.
Each guest will receive a welcome drink on arrival before being shown to their seat. Berry will begin the countdown to the event, and everyone will have at least one scone with jam and clotted cream, as well as a cup of English breakfast tea.
There will be official adjudicators present at the event. If the Guinness World Records are broken, each visitor will receive a medal.
Cath Kidston is donating ticket sales for the event to the Friends of the Elderly charity. The activation is being delivered by brand experience agency XYZ.