Having spent a lot of January discussing commemorative plaque schemes in conjunction with virtual tours and related projects got me thinking about a unique Blue Plaque that is not even blue. The plaque commemorating Dr. Samuel Johnson on his former residence in Gough Square (photo above) is unique because it is the only Blue Plaque in the City of London (the "Square Mile"). You might be scratching your head right now, recalling that you have seen other blue plaques in the City of London and, while they may have been blue (in contrast to this one), they were certainly not "Blue Plaques". The term has become ubiquitous now, with people using it as a catchall for all commemorations, but the "official" Blue Plaques were those put in place by the English Heritage Trust and their predecessors beginning in 1866 (https://www.english-heritage.org.uk/visit/blue-plaques/) in what is thought to be the first scheme of its kind in the world.
English Heritage has only had the job since 1986; from 1965 until then it was handled by the Greater London Counsel; before that the London County Council was in charge from 1901. But it was the Society of Arts (later the Royal Society of Arts) that originally took the scheme on and, although the first few plaques were blue, that colour was expensive and difficult to produce at the time, and so the chocolate brown variety was given preference. And it was the Society of Arts that erected Dr. Johnson's plaque here in 1876 as you can see spelled out in the lettering encircling the plaque itself. Only a few years afterwards, however, it was decided that the City of London would be in charge of their own commemorative plaque scheme; as a result this plaque is the only one of its kind in the Square Mile!