Four al-Qaeda inspired Britons, including a man of Indian origin, on Wednesday pleaded guilty to plotting a Mumbai-style attack on the London Stock Exchange, the American embassy and other targets during the run up to Christmas in 2010.
Mohammed Chowdhury, Shah Rahman, Gurukanth Desai and Abdul Miah pleaded guilty to engaging in conduct in preparation for acts of terrorism. Desai is of Indian origin.
The men, from London and Cardiff, were arrested in December 2010.
Five other men have pleaded guilty to other terrorism offences and all nine will be sentenced next week.
The men, from London, Stoke and Cardiff, were inspired by al-Qaeda in the Arabian Peninsular (AQAP) and used their English-language magazine Inspire as a guide.
They were inspired by the preachings of the recently-killed radical extremist Anwar Al-Awlaki.
It emerged that those who admitted planning to target the London Stock Exchange wanted to send five mail bombs to various targets during the run up to Christmas 2010 and discussed launching a "Mumbai-style" atrocity.
A hand-written target list discovered at the home of one of the men listed the names and addresses of London Mayor Boris Johnson, two rabbis, the US embassy and the Stock Exchange.
The conspiracy was stopped by undercover anti-terror police before firm dates could be set for attacks.
The terrorists met because of their membership of various radical groups and stayed in touch over the internet, through mobile phones and at specially arranged meetings.
They gathered in parks in a bid to make surveillance difficult.
The court heard that Chowdhury, 21, and his London accomplice Rahman, 28, were followed by undercover detectives on November 28, 2010, observing Big Ben, Westminster Abbey, the London Eye and the Palace of Westminster.
Chowdhury and Rahman admitted preparing for acts of terrorism by planning to plant an improvised explosive device in the toilets of the London Stock Exchange.
The men admitted the offences after a special hearing which allows a defendant to hear from the judge what sentence they may receive if they plead guilty on the eve of a trial.
Following the guilty pleas, DAC Stuart Osborne, from West Midlands Police's counter terrorism team, said: "We welcome the guilty pleas entered by all nine defendants today, following what was the largest counter terrorism operation of 2010.
