The 20-year old from north London planned to detonate an explosive device to access her office at 10 Downing Street, then attack her with a knife or a gun, an article on Reuters reports.

“We are talking about an individual that would have killed, injured and maimed a number of people including police officers and members of the public,” said Dean Haydon, head of the Metropolitan Police’s Counter Terrorism Command. 

According to the article, Rahman was arrested last November following a meeting with undercover officers posing as IS members. He had been planning the attack for two years and his determination increased when his uncle was killed in a drone attack last year.