Wahaca has confirmed all the restaurants it been closed after a suspected norovirus outbreak have now been reopened.
The restaurant said in a statement: "We are pleased to confirm that the final of our previously affected London restaurants is open and trading from lunchtime today, Tuesday 8 November. We continue to monitor the situation carefully and, as ever, will take any precautionary measure necessary to safeguard the health and wellbeing of our customers and team members."
It added it was "confident in our systems and processes" and "will continue to investigate how this suspected norovirus outbreak may have entered our restaurants and affected our staff and customers".
The Mexican food chain shut nine branches because of the infection, after hundreds of staff and customers fell ill, with Public Health England (PHE) launching an inquiry.
Soho, Covent Garden and Oxford Circus were the last to reopen after the weekend. The White City branch had reopened, but closed again on Saturday, before reopening once more on Sunday.
The other affected restaurants were Canary Wharf, Manchester, Cardiff, St Paul's and Brighton.
Last Thursday, when the news first broke, Deborah Turbitt, London deputy director for health protection for PHE, said the source of the norovirus outbreak was yet to be determined.
She said: "We have so far been made aware of 205 staff and 160 members of the public reporting illness, however these are unconfirmed ccases."
Norovirus is one of the most common stomach bugs, causing diarrhoea and vomiting, and can be caught at any time of the year.
It can spread rapidly in public places and can be caught through close contact with someone with the virus, touching contaminated surfaces or eating contaminated food that has been handled by an affected person who has not washed their hands.