Over the last 1,700 years, much of the riverside wall - traces of which were first identified 50 years ago - has been destroyed as London has grown.

However, three significant sections were uncovered by Museum of London Archaeology (MOLA) ahead of recent redevelopment along Upper and Lower Thames Street, which once formed the north foreshore of the River Thames.

These remains were extensively studied and recorded before being sealed in a protective layer beneath new office and retail buildings, where they will remain protected for future research in the event these are again redeveloped.

The little known riverside wall was a massive stone structure which is only now understood to have been connected to the landward wall, more famously known as the London Wall and still visible in parts of the modern City of London.

The purpose of the riverside wall has fascinated archaeologists and historians.

Duncan Wilson, Chief Executive of Historic England, said: “Even in a really dense city like London, built up over 2000 years, there are still mysteries to be revealed right beneath our feet.

“The riverside wall remains an intriguing element of Roman London which raises almost as many questions as it answers. The construction of the riverside wall effectively cut off the once bustling port, but why? It seems to suggest a major move towards defence at a time of uncertainty for the Roman provinces.”

Archaeologists suggest that as well as providing a defence against marauding tribes at a time of instability throughout the wider empire, the wall may have reinforced the status of Londinium. Together the landward and riverside walls formed a vast defensive ring around the city, unlike that of any other town in Roman Britain.

In some places the riverside wall incorporated reused monumental masonry, making it an important source of information for an understanding of architecture in Roman London, as well as Roman and medieval civil engineering and construction techniques.