Using other postcards and photos and noting things like chimneys, the state of the render falling off and condition of whitewash, I’ve determined by best estimate this rarely seen photo is likely dated 1921 and 1922.
Despite photos of an earlier era showing the Shuttle Row Building in worse condition, i believe this whitewash paintwork was an effort to clean up the building, perhaps even by the local authorities who were under some pressure about the living conditions there. Scratching at the surface, the roads are still muddy and filthy, chickens roaming free and the render even in this photo has fallen off the lower part of the building. Such early paint would not have been good or long lasting and its quite plausible that the very next year, after only 1 winter, the building looked patchy and perhaps by the second year after for very little of the whitewash to be remaining.
A travelling salesman sells his wares from the back of his horse and cart, to two interested women, likely living in Shuttle Row at the time.
By 1928, renovation work began on the building and in 1929 it was opened as the David Livingstone Museum.