This is the Bucklersbury Mosaic. One heavy presence of Roman culture among the people of Roman London was the existence of well-decorated architecture. The mosaic shown in this image was found in 1869 during the construction of a street. It is said to have been there from a private building in the AD 240s. It was most likely a bath suite or maybe even a dining room as mosaics were well fit in these areas of Roman Architecture. It is one of the more well-preserved stone pieces of London history as it has been fixed up and put on display for the public (the condition it is in as viewed in the image).
“Roman London History - Free Gallery.” Museum of London, www.museumoflondon.org.uk/museum-london/permanent-galleries/roman-london.
Bryan, Jessica. “Later Roman London, c AD 140 to c AD 410.” Archeology at Bloomberg, 2017. PDF.