An Islamic State fanatic plotted to assassinate Prime Minister Theresa May in a suicide attack on 10 Downing Street, a court has heard.
Naa'imur Zakariyah Rahman, 20, allegedly thought he was just days away from inflicting "lethal violence with blade and explosion" before his arrest last November.
But his plan was uncovered by an MI5 operative, who posed as a senior IS official in Syria, the Old Bailey heard.
On September 14 last year, Rahman was allegedly snared in Telegram chat with an MI5 role player, posing as an Amir in Syria.
The court heard Rahman asked him: "Can you put me in a sleeper cell ASAP?"
He told the agent he was under investigation because of his uncle.
When he asked for more information, he allegedly said: "I want to do a suicide bomb on Parliament. I want to attempt to kill Theresa May."
The next day, jurors heard he said: "My objective is to take out my target. Nothing less than the death of the leaders of Parliament."
The court heard Rahman went on to praise the Manchester arena bomber, saying he "did well".
He allegedly said he thought about wearing "a vest", driving past Parliament and "pushing the button" to "clear the entire block".
Jurors heard he said: "Everyone inside, including the Prime Minister would be dead."
Rahman is charged with preparing terrorist acts by conducting reconnaissance, recording a pledge of allegiance, and delivering a rucksack and jacket to be fitted with explosives.
Prosecutor Mark Heywood QC said: "His settled conclusion was that lethal violence here, directed at the very heart of the United Kingdom government, was the only effective way to pursue his intentions.
"Before his arrest prevented it, he was, he believed, just days away from his objective, which was no less than a suicide attack, by blade and explosion, on Downing Street and, if he could, upon the Prime Minister Theresa May herself."
The defendant, of Finchley, north London, is also charged with helping his friend Mohammad Aqib Imran, 22, to prepare terrorist acts.
He allegedly recorded a sponsorship video for Imran to join IS in Syria.
Mr Heywood said the men knew each other well, and shared the "warped ideology" of IS.
Rahman's uncle had joined IS in Syria and allegedly encouraged his nephew to attack the UK before he was killed in a drone strike, jurors heard.
Rahman denied two counts of preparing terrorist acts.
Imran, of Sparkbrook, Birmingham, has pleaded not guilty to preparing terrorist acts abroad and possessing a terrorist document on his Kindle entitled How To Survive In The West - A Mujahid's Guide 2015.