The mother and girlfriend of two Islamist terrorists have been convicted separately of failing to report plans for a terror attack.

Tasnia Ahmed, 21, from Tower Hamlets in east London, failed to report her then would-be terrorist boyfriend Al-Arfat Hassan to the police despite knowing he intended to carry out a mass casualty attack using a knife or a bomb, the Crown Prosecution Service (CPS) said.

Earlier this year drill rapper Hassan, 21, who used his music to “glorify” so-called Islamic State killings, was convicted after buying chemicals online to construct an improvised explosive device (IED) and possession of terrorist material – a video showing how to kill a prisoner with knives and how to make an IED.

He was jailed in February at the Old Bailey for five years with a further two years on licence.

One of Hassan’s teenage fans, a 17-year-old from Leeds, was sentenced to three and a half years in prison for failing to disclose his knowledge of Hassan’s terrorist activities and possessing terrorist material – the same video that Hassan had possessed.

This defendant can now be named as Sameer Anjum, after reporting restrictions in the case were lifted.

Hassan and Anjum had been exchanging extremist messages, graphics and voice notes almost daily over a number of months, the CPS said.

Anjum’s mother, Nabeela Anjum, from Roundhay, Leeds, has been convicted of failing to disclose information about Hassan’s activities, which she learned of from her son.

The 48-year-old was found guilty on Tuesday following a trial at Leeds Crown Court. She has been bailed until her sentencing on a date yet to be confirmed.

Prosecutors said the jury was shown detailed messages where Nabeela Anjum pleaded with her son to stop communicating with Hassan.

In one message following Hassan’s arrest, she told him: “Please get rid of everything from your phone…”

Tasnia Ahmed in particular knew of Hassan’s extremist beliefs. He had repeatedly told her of his intention to carry out a knife or bomb attack

Ahmed was found guilty following a separate trial at Woolwich Crown Court which concluded on April 25. She will be sentenced at the same court on June 3.

The CPS said evidence presented during Ahmed’s trial showed that she had been in a relationship with Hassan since October 2021, and exchanged more than 85,000 text messages over three months.

In some of these messages Hassan revealed his desire to carry out a terrorist attack, writing: “I have to get it done, I know the perfect spot where millions, millions of people are…”

Ahmed told him that he would “die for a good cause,” adding: “I’ll support you if that’s what you really want.” She also wrote she would buy him a better knife.

Mobile phone evidence showed Ahmed and her cousins referred to Hassan as “bomb man” and a “terrorist” in their exchanges, making it clear that she had been aware of her partner’s terrorist activities, the CPS said.

Hassan’s phones were seized at Heathrow airport in February 2022, and he was arrested in March 2022.

Ahmed and Anjum were not known to each other.

Nick Price, head of the CPS Special Crime and Counter Terrorism Division, said: “These two women jeopardised the safety of the public by blindly choosing not to report acts of terror openly being discussed and planned by those known to them – that is criminal behaviour and illegal. When presented with the evidence in court, the juries in both cases found that these women had acted unlawfully and convicted them.

“Tasnia Ahmed in particular knew of Hassan’s extremist beliefs. He had repeatedly told her of his intention to carry out a knife or bomb attack – she indulged this and spoke about it as if it was normal behaviour. Nabeela Anjum sought to protect her son, but in trying to do so, she found herself armed with knowledge about terror activities that she knew needed to be reported.”

Detective Chief Superintendent James Dunkerley, the head of Counter Terrorism Policing North East, said: “This demonstrates how important it is to report serious information to the police. We are all under a legal duty to report to the police any information which we know or believe might be of assistance in preventing an act of terrorism.

“You may think that you are helping and protecting someone by withholding information, but you are not, and it can make things worse.”