Over several weeks, MI5, along with Scotland Yard and West Midlands Police, had been pursuing the case.
The two men arrested for the plot - Naa'imur Zakariyah Rahman, 20, from north London and Mohammed Aqib Imran, 21, from Birmingham - will attend a preliminary court hearing at Westminster Magistrates' Court on Wednesday morning.
10 Downing Street is the location of the prime minister's office.
It is not clear how Imran and Rahman planned to get through the fortified gates and armed police officers guarding Downing Street.
Beyoncé surprises Colin Kaepernick with Sports Illustrated's Muhammad Ali Legacy Award
Music icon Beyonce introduced the 30-year-old, who last played during Week 17 of the 2016 National Football League season. Although many have voiced their support for Colin, the American athlete has been met with quite a bit of criticism too.
Addressing the Cabinet, Mr. Parker reportedly said Isis had been defeated in Syria and Iraq but was continuing to orchestrate attacks on the UK.
The details come hours after an independent review suggested the deadly suicide bombing at Manchester Arena may have been prevented if information had been handled differently by British police and intelligence services.
Bomber Salman Abedi killed 22 people when he blew himself up outside an Ariana Grande concert in Manchester.
But Anderson, a former terrorism law reviewer asked by the government to review the recent spate of terror attacks, concluded there is "no cause for despair". The then prime minister, John Major, was inside but was not hurt. The same report found that the ringleader of the June London Bridge attack was actively under investigation at the time.
Security measures were introduced in the 1970s but were increased in the 1980s as the threat from Irish republican groups grew.