An Islamic State terrorist has been found guilty of a plot to behead the Prime Minister in a suicide attack on the heart of Government.

Naa’imur Zakariyah Rahman, 20, planned to bomb the gates of 10 Downing Street, kill guards and then attack Theresa May with a knife or gun.

He had pledged allegiance to IS and collected what he thought was an explosives-packed rucksack when he was arrested last November.

Naa’imur Zakariyah Rahman court case
Naa’imur Zakariyah Rahman (left) and Mohammed Aqib Imran in the dock (Elizabeth Cook/PA)

The drifter, originally from Birmingham, thought he was being helped by an IS handler when in fact he was talking to undercover officers.

Following an Old Bailey trial, Rahman, from Finchley, north London, was found guilty of preparing acts of terrorism in Britain.

Midway through the trial, he admitted helping his friend Mohammed Aqib Imran to join IS in Libya by recording an IS sponsorship video.

Imran, 22, from south-east Birmingham, was found guilty of having a terrorist handbook after the jury deliberated for 13 hours.

The jury is still deliberating on a charge against Imran of preparing terrorist acts abroad.

Rahman was snared by a network of undercover counter-terrorism officers from the Metropolitan Police, the FBI and MI5.

The trial had heard how Rahman was encouraged by an uncle who travelled to Syria to fight and was killed in a drone strike last June.

Rahman came to the attention of police in August last year when he was arrested on suspicion of sending indecent images to underage girls, but never charged.

An examination of his mobile phone raised concern he may be harbouring extremist views.

After his uncle’s death, he became even more determined and turned to the internet for help in his attack plans.

Naa’imur Zakariyah Rahman court case
A rucksack belonging to Naa’imur Zakariyah Rahman (Met Police/PA)

Rahman made contact with an FBI agent posing as an IS official online, who introduced him to an MI5 role-player.

The defendant revealed his plans, saying: “I want to do a suicide bomb on Parliament. I want to attempt to kill Theresa May.

“There are lorries here with big gas tankers, if a brother can drive it next to Parliament I will bomb.”

He later described using a suicide belt, a drone, an IED and poison, referred to as “P” or “curry mix”.

By early November last year, he appeared settled on an attack on 10 Downing street with a suicide bomb, gun or knife.

He told an undercover officer: “[God willing] will be very big if I’m successful. I can’t mess up. I can’t get [martyrdom] if I get caught.”

On November 18 last year, Rahman carried out reconnaissance around Whitehall.

Two days later, he bought a rucksack from Argos before meeting an undercover officer in Brixton for it to be fitted with explosives.

In November 28 last year, the officer handed back Rahman’s rucksack and coat –  now packed with dummy explosives – and replica pepper spray.

Rahman told the officer he was “good to go” but was arrested as he walked away carrying the fake bomb in Kensington.

Imran denied all the charges against him and Rahman had denied preparing terrorist acts.