All Wahaca restaurants that were voluntarily closed following a suspected outbreak of norovirus are expected to reopen as of lunchtime today.
The Mexican restaurant group closed nine restaurants after more than 200 staff and 160 diners started to fall ill during the week before last.
The first of the restaurants to close was in Manchester on 26 October, and Wahaca took action to close eight others when it became clear that it was not an isolated incident.
The eight other restaurants were in London's Soho, Covent Garden, Oxford Circus, St Paul's, White City and Canary Wharf, as well as Cardiff and Brighton.
Following the suspected outbreak of the virus, also known as the winter vomiting bug, Wahaca contacted officials at Public Health England and environmental health offices and carried out anti-viral deep cleaning at all of its restaurants, whether affected or not.
It said it also ensured that staff members who had reported illness remained off site until their symptoms had ceased for at least 48 hours.
The business has also cancelled its annual Day of the Dead fiesta and refunded all ticket buyers.
In a statement, co-founders Thomasina Miers and Mark Selby said: "We are incredibly sorry that people have been unwell. In the 9 years since we first opened Wahaca we have never had such an unprecedented incident, and we are doing everything we can to get to the bottom of how this may have happened."