Anyone who has spent a significant amount of time in London will no doubt have strayed across a building that bears a distinctive circular blue plaque.
There are about 880 of these commemorative tablets dotted around our capital and their purpose is to celebrate the link between a well-known person and the building.
The scheme was founded by the Royal Society of Arts, and was set up way back in the 1800s. In fact, the very first plaque was erected in 1867 to commemorate the poet Lord Byron at his birthplace in Cavendish Square.
Back then the plaques weren't necessarily blue; a number of colours and borders were trialled before the London County Council, who took over the scheme in 1901, eventually settled on today's recognisable colour and design. If you keep your eyes peeled, there are still some old green, brown, white and terracotta plaques to be found in the centre of town.
By 1965 when the LCC was abolished, almost 250 plaques had been installed across inner London. The scheme was then taken over by the Greater London Council, which widened the coverage to outer London including boroughs such as Richmond. A few years later, in 1986, The English Heritage took over and have put up a further 360 plaques in just under 30 years.
Since its outset the project has helped raise awareness of some of London's most significant buildings, and in some instances, has saved them from being demolished.
It's always fascinating to come across a blue plaque and read which significant figure lived or stayed there and for how long.
Wherever you are in the capital, there will inevitably be a plaque nearby as they can now be found in all but three of London's boroughs. Why not see how many you can spot while you're out and about?
If you'd rather find out which blue plaques are nearby and discover exactly where they are, you can do a search on the English Heritage website. Search by keyword, postcode, the London borough, the organisation, or the year erected. For example, if you're near the West End, there are a whopping 302 plaques in the borough of Westminster alone, including Ian Fleming and John Lennon.