The Justice Secretary, writing exclusively in the Daily Express as he ushers in a new law to protect the public from radicalised fanatics, pledged: "No terrorist should be released early only to kill and maim on our streets. "Protecting the public is the Government's first duty. From today, terrorist offenders will be released before the end of their sentence only if the independent Parole Board is satisfied they no longer pose a threat.
"And they will face the strictest possible conditions and monitoring upon release."
The emergency legislation, which became law in just 15 days, applies to offenders sentenced for crimes, including training for terrorism, membership of a proscribed organisation and the dissemination of terrorist material.
Crucially, it ends the automatic release halfway through their terms of offenders who receive standard determinate sentences.
Instead, they must spend a minimum two thirds of their punishment behind bars before a panel of judges and psychiatrists at the Parole Board reviews their release.
Those who are considered still to be a threat to public safety will spend the rest of their sentence in prison.
The Terrorist Offenders [Restriction of Early Release] Bill, which received Royal Assent last night, was hurried through after outrage over dangerous offenders being released automatically.
The legislation, coming into force just before the next prisoner is freed, means around 50 terrorist prisoners already serving sentences will stay in jail.
Mr Buckland acted after a string of high-profile, radicalised prisoners were let out and went on to commit atrocities. In November two people were killed at London Bridge by convicted terrorist Usman Khan, who had only served half of his sentence . Khan, 28, was sentenced to indeterminate detention for "public protection" with a minimum jail term of eight years.
Justice Secretary Robert Buckland (Image: TOLGA AKMEN/AFP via Getty Images)
But he wrote a remorseful letter to the Home Office asking to participate in a de-radicalisation programme, saying he was "immature" when he committed offences and he wanted to be "a good citizen".
Khan was released in December 2018 on conditions requiring him to wear an electronic tag. He was still on licence when he killed Jack Merritt, 25, and Saskia Jones, 23, and injured three others in a stabbing frenzy before being shot dead.
Prisoners due to be freed in the coming days and weeks include Sunderland shopkeeper Mohammed Zahir