The Easter Fair.
For anyone unsure of the location (younger folks), the two buildings in the background are still with us today on King William St, the Nat West Bank to the left and what was until a decade or so ago, Burtons the Tailors, with New Market St running between them. Through the spokes of the big wheel, you can just see the pitched roof of the fish market and part of the old clock tower.
The area where the crowds are, is marked on maps from the past as Market Place.
Courtesy of John Eddleston