However it was not until 1867 that the first plaque was put in place, under the auspices of the Royal Society of Arts. This was put on Byron's birthplace in Holles Street, Westminster. The house has since been demolished. The earliest two surviving plaques date from 1875. Ironically one of them, in Gerrard Street, Covent Garden, is almost certainly on the wrong building and honours the home of the next-door neighbour of the poet John Dryden. The other, in King Street, St James's, marks the lodgings of the future French emperor Napoleon III, who stayed there in 1848 just before crossing the Channel to make his own contribution to the revolution of that year.
The Royal Society of Arts continued their scheme and, by 1901, there were 36 plaques in existence. The scheme was taken over in that year by the London County Council and when, in 1965, the LCC became the Greater London Council, the new organisation took responsibility for the plaques. In 1985, with the abolition of the GLC, a new home had to be found for the Blue Plaque scheme. The Local Government Act of that year gave responsibility to English Heritage, who have continued to erect plaques regularly.
There are now close to 700 official plaques in existence, most to individuals but a few to historic buildings or events. Not all the plaques, particularly the early ones, are the familiar blue but the majority follow the well- known design of white lettering on a blue ground. When, recently, a plaque was erected to Jimi Hendrix in Brook Street, Mayfair, there was some talk of making it purple to recall his song "Purple Haze" but, finally and perhaps boringly, it was decided to stick with the traditional design.
There are a few simple rules which English Heritage follows in choosing who to commemorate with a blue plaque. The individual must have been dead for 20 years or the centenary of his or her birth must have passed. The person must "have made some important positive contribution to human welfare or happiness". The recipient of the plaque must have sufficient fame that "the well- informed passer-by" will recognise his or her name.
Working within these simple rules the official blue plaque scheme has celebrated an extraordinary diversity of people. The great and familiar names of English history and culture are nearly all represented. Yet one of the pleasures of investigating the stories behind the blue plaques is coming across lesser-known men and women of achievement.
For example there is a house in George Street, off Edgware Road, where the pioneer nurse Mary Seacole lodged. Everyone has heard of Florence Nightingale (plaque in South Street, W1) but not enough people have heard of Mary Seacole, whose story is, in many ways, more remarkable. She was born in Jamaica, the daughter of a free black woman and a Scottish army officer, and travelled to Britain at the time of the Crimean War to offer her services as a nurse to the Government. She was turned away, doubtless because of her colour. Undismayed she financed her own journey to the battlefields and established a nursing station at Balaclava, far closer to the front line than that of Florence Nightingale. Bankrupted by the war, she recovered her finances through public subscriptions and the publication of a best-selling book, The Wonderful Adventures of Mrs Seacole in Many Lands.
Behind the simple and classic design of the familiar blue plaque lie stories, like that of Mrs Seacole, of some of the most remarkable people to have made their home in London.
Nick Rennison is author of `The London Blue Plaque Guide' (Sutton Publishing, pounds 9.99)