The Bloomberg tablets are a collection of 405 preserved wooden tablets that were found at the site of the Bloomberg building in the financial district of London. Excavations of the site took place between 2010 and 2013, after which the current Bloomberg building was constructed on the site of the archaeological dig.
The tablets are the earliest written documents found in Britain, dating from 50 to 80 AD in the early Roman period. Notably, these tablets predate the Vindolanda tablets, which were previously the earliest writing examples found in Britain, dating to 100 AD or later.
The Bloomberg site consists of three acres in what was the Roman city of Londinium. The archaeological site had previously yielded a 3rd-century Temple of Mithras, which was partially excavated in the 1950s, but this effort was incomplete, and Bucklersbury House, a 14-storey modernist office block, was built atop the site in 1953. However, the demolition of the Bucklersbury building in 2010 gave archaeologists a chance to reopen the dig. Between 2010 and 2013, a multitude of artefacts were discovered at the site, including the Bloomberg tablets, discovered buried 40 feet underground.
The Bloomberg tablets were an unexpected find, as organic material such as wood and leather tends to rot away and disintegrate with time. The tablets were preserved by the thick, wet mud generated by the underground river Walbrook, which limited the exposure of the tablets to oxygen.
The tablets were originally made of wood and wax, though only the wood was preserved and recoverable. A typical tablet would have been made of a thin piece of wood, 15–25 cm wide, with a rectangular depression carved into the centre. Warm beeswax, blackened by the addition of atramentum, would then be poured into the centre depression and allowed to cool. Once the wax had set, a metal stylus would be used to scratch letters into the wax, showing a lighter colour against the darker wax.
These wax tablets could also be recycled, in that the tablet could be heated (to approximately 50 °C), allowing the wax to soften and reform a smooth writing surface. The tablets were likely made from wood recycled from barrel staves, and often were made in diptych style, where two tablets were loosely linked and could fold together to close, like a book with only two pages, protecting the soft wax on the inside.
Although the wax from the tablets was not preserved, small scratches left on the surface of the wooden tablets allowed for a recreation of the original writing content. These scratches, though perhaps not identifiable with the naked eye, can be visualised and digitally recreated with the assistance of technology. To make the digital recreation of the writing, photographs were taken using different angles of light and thus casting different shadows upon the tablet surface. Once compiled, these pictures gave a precise view of the surface contours of the tablets, the impressions made in the wood, and thus a look at what was written on the tablet. However, since these tablets were made to be reusable, several overlapping messages may be present on the tablets, making it even more difficult to separate and translate the many messages.
Ninety of the Bloomberg tablets have been translated. This is the highest number of translated artefacts from any archaeological site in London, surpassing the previous record of 19. The tablets were translated by Dr. Roger Tomlin, an expert in Roman cursive, the writing style in which the tablets were written. Tablets vary in content, including the oldest financial document from the city of London (dating to 8 January 57 AD), legal documents including a judge calling a pretrial hearing, and educational material. One tablet shows the alphabet written out, indicating the presence of perhaps the first school in Britain. Additionally, among the tablets there are over 100 names of people of all different professions and social classes who lived in London at the time, such as slaves, merchants, soldiers, and politicians. One prominent figure that is named is Julius Classicus, who was a commander in the Roman auxiliaries. One tablet contains the first mention of the name of the city of London, more than a half a century earlier than what was previously thought to be the first naming of London, in the Annals of Tacitus.
Although current technology and methods have allowed for recreation and translation of a number of the tablets, the vast majority of them remain as-of-yet unreadable. Thus, to keep these tablets in prime shape for future analysis, efforts are being made to keep these artefacts preserved. Preservation included a combination of immersion in polyethylene glycol (PEG) and freeze drying.
While some of the tablets are being preserved for future study, a number of them will be displayed in a museum exhibit entitled “London Mithraeum” located on the first two floors of the Bloomberg European Headquarters, which opened in November 2017. 
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