Three were recalled to prison after disclosing "risk-related information", while the fourth didn't comply with their polygraph licence condition, the Ministry of Justice (MoJ) document revealed.

Compulsory lie detector tests for terrorists convicted of a relevant offence who are granted parole were introduced by the Counter-Terrorism and Sentencing Act 2021, which was drawn up after the 2019 Fishmongers' Hall attack.

Usman Khan, 28, had been attending a conference on prisoner rehabilitation when he stabbed to death Cambridge University graduates Jack Merritt, 25, and Saskia Jones, 23, who were also at the event.

The convicted terrorist - who planned to blow up the London Stock Exchange and build a training camp in Pakistan-controlled Kashmir - had been out of prison on licence for more than a year after serving half of a 16-year sentence.

The MoJ report said 46 people have been subject to the polygraph licence condition between 29 June 2021 and 30 June 2023.

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A total of 88 lie detector tests have been carried out on 39 people, with the result classified as a "significant response" in 31 instances, or 35% of the examinations.

"A significant response is an examination result interpreted as 'deceptive', where the examiner concludes the individual has not been telling the truth when answering one or more of the polygraph examination questions," the report said.

"Disclosures of risk related information", which are considered alongside other "risk relevant information", were recorded in 63 instances, or 72% of examinations.

"In three cases this has led to individuals being recalled," the report said.

"A lack of compliance with the polygraph licence condition by a fourth individual also contributed to their recall."

The Counter-Terrorism and Sentencing Act created a new category of "serious terrorist offences" amid concerns offenders convicted of planning attacks were receiving relatively light sentences.

It said those found guilty under the category should face a minimum of 14 years in prison, with an extension period to be served on licence of between seven and 25 years, unless there are "exceptional circumstances".