The attack signalled the start of another bombing campaign against Londoners.
Fifty years ago, the House of Commons descended into darkness and chaos after an explosion went off in the heart of the chambers.
A 9.1 kg bomb was planted in Westminster Palace by the IRA, injuring 11 people and signalling the start of a renewed bombing campaign in England.
It took just seconds for a fire to begin ripping through the heart of the UK’s democracy, with the 900-year-old central hall at the heart of the attack.
The year of 1974 was already one the deadliest in the IRA’s British mainland bombing campaigning.
A few months earlier a bomb exploded on a coach carrying soldiers, killing 12 people.
Another 26 people towards the end of the year in attacks on pubs in Guilford, Birmingham and the Tower of London.
Thankfully no one was seriously injured in the attack on Westminster, as bystanders rushed to help MPs and other staff members caught up in the attack.
But a gas main was fractured in the blast only adding fuel to the blaze, with smoke shrouding famous landmarks including Big Ben.
David Steel, the then-Liberal Chief Whip, was in the building when the device detonated.
He told the BBC: ‘I looked through Westminster Hall and the whole hall was filled with dust.
‘A few minutes later it was possible to see flames shooting up through the windows.’
Just before 8.30am, a man with an Irish accent phoned Press Association, giving the receiver a six minute warning an explosion will go off in Westminster.
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Police recognised the IRA code word used, and with no exact location of the bomb given, there was a scramble to evacuate everyone safely.
Just minutes later, the bomb exploded in an annex in the corner of Westminster Hall before everyone was able to be evacuated.
Construction worker Patrick Arundel’s hand was injured by broken glass.
He told the New York Times he heard a woman with a broken leg pleading for help.
‘I got a ladder and climbed up to the first floor. I told her to try to crawl to the window but she had a broken leg,’ he said.
‘I could not get in because of the smoke, but a fireman came and pulled her out.’
The blast was so loud firemen at Westminster and Lambeth station heard the explosion.
Centuries of dust which were laying stagnant in the hall were dislodged.
More than 100 firefighters were needed to help contain the blaze, with major concern being placed on the hall as it was considered the most historic part of the Houses of Parliament.
But the attack only strengthened the resolve of lawmakers, with Jeremy Thorpe, the end-leader of the Liberal party saying: ‘This House will be not bombed into a decision, but will negotiate peacefully with me of peace.’
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