This is when Downing Street had gates fitted and why were they erected
However, the gates failed to prevent the IRA from launching mortars into the street from a parked van in Whitehall in 1991.
This lead to former Prime Minister, John Major who was in charge at the time, along with his colleagues to shelter under the cabinet table, reports The Guardian.
New barrier put up to protect Downing Street in 2004
A hydraulic barricade was officially installed in 2004 to protect Downing Street from suicide bombers, police confirmed at the time.
A Scotland Yard spokesman said protective addition would not replace the previous temporary barriers which “damaged” the view of the famous political street for tourists and Londoners.
The spokesman said: "We can confirm work is ongoing at Downing Street as part of an ongoing security review.
"It is not in response to any specific threat or intelligence."
The barriers were designed to prevent vehicles containing explosives from "ramming" into the street where the prime minister and chancellor live.
A car has crashed into the gates of Downing Street and a person has been arrested.
Whitehall was consequently closed and police originally set up a cordon following the incident.
But in a statement released nearly two hours after the crash, the Metropolitan Police said: “A small cordon remains in place outside Downing Street after a car collided with the gates earlier this afternoon.
“The incident is being dealt with by local officers in Westminster and isn’t currently being treated as terror-related.”
A man was arrested by armed officers on suspicion of criminal damage and dangerous driving, the police have said.
A Metropolitan Police statement said: “At approximately 16:20hrs on Thursday, 25 May a car collided with the gate of Downing Street on Whitehall.
“Armed officers arrested a man at the scene on suspicion of criminal damage and dangerous driving. He has been taken into custody.
“There were no reports of any injuries.
“Enquiries are ongoing to establish the circumstances.”