Discovered by Peter Marsden on 6 September 1962, the first Blackfriars ship became the earliest known indigenous seagoing sailing ship to be found in northern Europe, dating back to the 2nd century AD. The wreck is dated to a period of great Roman expansion and construction. Found between Blackfriars Bridge and Blackfriars Railway Bridge during the construction of a new riverside wall, the Blackfriars I generated controversy since it appeared to match a native Brythonic shipbuilding style instead of a traditional Roman style.
The Blackfriars I was built frame-first, meaning that the frame of the ship was built before building the rest of the ship. This method was much faster and saved wood, and was advanced for the period. Marsden described the ship as having a carvel-built hull caulked with hazel twigs, mast-step and thick floors secured with nails. On the ship, a bronze votive coin of the Emperor Domitian was found in the mast of the ship. In addition, it was discovered that the ship was wrecked while carrying cargo that consisted of 26 long tons (26 t) of Kentish ragstone, a type of building stone. With further findings about the area of operation of the ship, Marsden suggested Blackfriars I was used for constructions purposes. The rest of the cargo included: two pottery sherds, a wooden mallet, and a piece of leather. Marsden was able to conclude, using the location and position of the wreck that it crashed into another vessel, a collision which was responsible for the ship sinking.
The Blackfriars II was discovered in June 1969 east of Blackfriars Bridge. The ship was carrying a cargo of brick when it was wrecked. Marsden and R. Inman excavated the wreck. Their findings showed that the cargo included new red bricks, pipes and pottery that dated back to 1660–80. With this information, Marsden was able to conclude that the ship was carrying materials meant for rebuilding London after the Great Fire of 1666. The techniques used to build this ship led Marsden to believe that the state of contemporary knowledge of shipbuilding was insufficient for dating small boats.