The first Act was enacted in 1974 following the IRA bombing campaigns of the early 1970s . The Act was introduced by Roy Jenkins , then Home Secretary , as a severe and emergency reaction to the Birmingham pub bombs . The apparent chronology was that there were pub bombings by the IRA in Birmingham on 21 November 1974 . 21 people died and 184 were injured . There was a strong desire to respond to what was perceived as " the greatest threat to the country since the end of the Second World War . " ( H.C. Debs . Vol . 882 col. 743 28 November 1974 , Mr. Lyons . ) The conception of the Bill was announced on 25 November , when the Home Secretary warned that : " The powers ... are Draconian . In combination they are unprecedented in peacetime . " ( Ibid . col. 35 25 November 1974 , Mr. Jenkins ) . Parliament was supportive and had passed the Bill by 29 November , virtually without amendment or dissent . The Bill passed through the Commons on 28 and 29 November and passed through Lords on 29 November . In fact , much of the Bill had been drafted in secrecy during the previous year , as shown in the only full length television commentary on the legislation by Clive Walker
pub bombings
Birmingham pub bombings
Prevention of Terrorism Acts