Heston Blumenthal's two-Michelin-starred London restaurant Dinner has been closed following an outbreak of norovirus.
A total of 23 diners and 21 members of staff were taken ill with suspected cases of the virus at the restaurant in the Mandarin Oriental hotel.
The 44 people are thought to have fallen ill over a six-day period stretching from 16 January and 21 January 2014.
A spokesman for Westminster City Council said that health inspectors conducted tests following the outbreak and confirmed some positive samples of the virulent stomach bug norovirus late last week.
The spokesman said on Friday 31 January: "We had a number of tests going on this week and came back yesterday. Looking at the general charateristics of the outbreak we are concluding that it is norovirus."
In a statement, a spokesperson for the restaurant said: "Over the last few days we were contacted by some guests who reported feeing unwell. As ever, the safety of our guests is our primary concern and in compliance with our stringent health and safety protocols we immediately contacted our Environmental Health Officer.
"The EHO conducted a full investigation and all swabs and tests of initial tests that had been returned proved negative. During the winter months many factors can contribute to illness and we had no indication that any of the communication from our guests was food related. EHO informed us that the situation was contained and advised closure was not necessary.
"After a six day period of quiet we were then contacted by another guest who felt unwell shortly after they had dined with us and we immediately contacted the EHO again. More results came back which found the winter flu bug in a total of five people comprising guests and staff. We have decided to close the restaurant to carry out the appropriate measures to ensure the environment is completely safe and norovirus free. We apologise for any inconvenience caused to those guests whose bookings have been cancelled however we understand how contagious this winter flu bug can be and will take every precaution necessary to protect our guests."
It is not the first time that one of Heston Blumenthal's restaurants has been affected by an outbreak of Norovirus. In 2009, his three-Michelin-starred Fat Duck in Bray was closed for two weeks after hundreds of diners were hit by the illness.
A 2011 report, published online in the journal Epidemiology and Infection, said the Fat Duck norovirus outbreak was the biggest at a restaurant ever recorded.
Norovirus is, as its name suggests, a virus, but it can be transmitted by contaminated food. It is highly infectious and outbreaks are common in semi-closed environments such as hospitals, nursing homes, schools and cruise ships. Transmission is person to person or through contaminated food such as shellfish.