Thursday, June 06, 2024

City of London: 'Ring of Steel'

Police Sentry Box
A City of London police sentry box.

Walking through and around the City of London you may notice that roads, entering the City, narrow and concrete islands have, usually empty, Police sentry boxes on them. 

These sentry boxes are a remnant of far more dangerous times. They were put in place, along with narrower roads and CCTV cameras, as a response to the IRA threats to the City of London from the 1970s through to the 1990s. This initiative became known as the 'Ring of Steel'.

But, this wasn't the City of London's first form of protective security. For that we must go back to the founding of Londinium. 

Roman Wall
The City of London's original defensive ring.

The Romans constructed a wall, many parts of which are still visible, to protect early Londinium from invasion from the Picts, who had invaded northern Britain and overrun Hadrian's Wall. 

To further protect Londinium the Roman's increased fortifications along the wall, as well as increasing the wall's height.

Various Wards were also created within the City walls, ensuring that communities were linked and security could be maintained. These community links are still as important today for keeping the City of London safe.

Terrorism became an issue for the City of London, and London as a whole, when Irish Republicans began a bombing campaign between 1867 and 1885. This was followed by Militant Suffragette actions, along with Anarchist attacks.

The Irish Republican Army started a limited campaign between 1939 and 1940, which became known as the 'Sabotage Campaign',

The most deadly attacks began in 1973 and would continue until 1997, when the Provisional Irish Republican Army began a sustained campaign during what was called 'The Troubles'. This was further exacerbated by attacks related to Middle East politics and more Anarchist attacks.

Police Sentry Box and Police Car
The City of London's 'Ring of Steel'.

It was during the 1990s that a new 'Ring of Steel' was put in place. This involved the narrowing of roads and the adding of small chicanes, which forced drivers to slow down. Concrete medians were also installed, each with a police sentry box manned by armed police. Some roads were closed to traffic altogether.

CCTV cameras recorded vehicles entering, and leaving, the City of London. One of the measures, now used throughout the world, was Automatic Number-Plate Recognition (ANPR) which was developed in the City of London. Today, the whole of London has traffic monitoring systems which are constantly viewed by police. This data is kept for five years.

Some dissident members of the Real Irish Republican Army and Islamic terrorism has continued to attack locations within the City of London, London and the UK, up to the present day.

Police Sentry Box
Keilyn in a police sentry box.

As new threats are detected new technology evolves. Cameras are moved, upgraded or more are installed. As the City of London changes, with roads rerouted, new businesses moving in or new infrastructure being constructed the 'Ring of Steel' adapts, doing its best to keep us safe.


  1. Who knew it went back that far. This site is a wealth of information.

    1. Thank you. I try to add some of the more obscure things.