Site: Holmes & Watson - Criterion (2 memorials)
W1, 224 Piccadilly, 224, Criterion Restaurant
The Criterion Restaurant is on the ground floor with the entrance at the left of our photo.
The meeting at the Criterion took place on New Year's Day in 1881, 72 years and 2 days before the first, lost, plaque was erected. The current plaque, erected to mark the centenary of the meeting, is inside, on the wall to the right, before the tables begin. It was brought to our attention by Londonist.
The meeting at the Criterion is described in the first Sherlock Holmes story "A Study in Scarlett" published in 1887. See the plaque at Barts Hospital for the actual meeting of Holmes and Watson.