Pubs and restaurants would stay open, but those across London would only be able to enjoy a drink or meal out with their household.
Mr Khan told Sky News on Wednesday: “Across our city… the average over the last seven days is about 90 per 100,000.
“All the indicators I have, hospital admissions, ICU occupancy, the numbers of older people with cases, the prevalence of the disease, the positivity are all going the wrong direction.
“Which means, I’m afraid, it’s inevitable over the course of the next few days London will have passed a trigger point to be in the second tier.”