(Photograph) - The dome of St Paul's cathedral dominates the mid-18th century London skyline in this detail from a painting by Giovanni Antonio Canal, better known as Canaletto.
Famous for his highly detailed views of Venice, Canaletto came to London in 1746, where he used the same precise style to record the capital's fashionable buildings and river views, including this painting which presents the River Thames on the day of the Lord Mayor's Show.
This annual celebration to mark the election of a mayor of the City of London has been held with only a few interruptions since 1215. This year's show, to be held tomorrow, will feature a procession through the streets. But as we can see from Canaletto's painting, the river played a far more important part in the celebrations 250 years ago, reflecting its central place in the life of the capital.
When Canaletto visited London, the Thames was the city's airport and bus network rolled into one, carrying people and trade from abroad and being used as an everyday route by Londoners crossing their city. While the wealthy and powerful were carried in the equivalent of private jets - the lavishly decorated barges we see in this picture - ordinary citizens would have used the hundreds of small boats which ferried people across.
As well as the mayor and aldermen, the water-borne procession in the painting would have included boats representing the City's livery companies and guilds, with ceremonial clothes and decorations expressing the wealth and status of the various crafts and trades - much as big companies today mke themselves visible at trade fairs.
This colourful crowd of boats observed by Canaletto followed in the long tradition of dressing boats to impress, dating back to the medieval mayors who travelled up the river with drummers, trumpeters and standard bearers.
In the early years of the 17th century, fake "Indian islands" were put on display in the Thames and a lion and camel were paraded through the streets.
When Canaletto arrived, there was only a single bridge across the river, London Bridge. But his visit came at the beginning of a time of change. Westminster Bridge was opened in 1850 and a few years later the old medieval gates, such as Moorgate and Aldgate, were demolished and the city reached out to the fashionable new towns of what we now know as the West End.
Canaletto's paintings are a record of what was considered voguish in the early 1750s in London. He was acting as a kind of architectural fashion photographer of the stately homes and pleasure gardens of his patrons. The accuracy of his work reflects his use of the camera obscura, a device which reflects an image on to ground glass so it can be precisely traced.
In 1755, Canaletto returned to Venice, where he once again painted the dramatic and idealised views of the city that had made him famous, with the English aristocracy among his most enthusiastic collectors. He died in Venice in 1768.
Lord Mayor's Show: www.lord-mayors-show.org.uk Online art encyclopedia: www.artcyclopedia.com National Gallery: www.nationalgallery.org.uk l Lord Mayor's Show, page 27