Naa’imur Zakariyah Rahman has been charged with scheming acts of terrorism and was remanded in control during a conference during Westminster Magistrates’ Court.
The 20-year-old, of Ballards Lane, in Finchley, north London, is also charged with assisting another man, Mohammed Aqib Imran, ready terror.
Imran, 21, of Ombersley Road, in a Sparkbrook area of Birmingham, also seemed in justice charged with perplexing to join Islamic State and scheming acts of terror.
He too was remanded in custody.
The pair, who were arrested in armed military raids in London and Birmingham final week, will seem during a Old Bailey on 20 December.
MI5 conduct Andrew Parker briefed Cabinet ministers with sum of a purported tract to murder a Prime Minister on Tuesday.
It came as a confidence group suggested it had prevented nine apprehension attacks in a UK in a past year.
Downing Street is stable by armed military officers and distant from a open by fortified gates.
Security measures were introduced in a 1970s though were increasing in a 1980s as a hazard from Irish republican groups grew.
In 1991, a IRA launched a homemade trebuchet explosve conflict on Number 10 and a device landed in a behind garden.
The afterwards primary minister, John Major, was inside though was not hurt.