Four radical Islamists have admitted an al Qaeda-inspired plot to detonate a bomb at the London Stock Exchange.
The Muslim fundamentalists' group 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 found at one of the defendant's homes listed the names and addresses of London Mayor Boris Johnson, two rabbis, the American Embassy and the Stock Exchange.
The total of nine men admitted various terror crimes at Woolwich Crown Court and will be sentenced next week.
"Lynchpin" Mohammed Chowdhury, 21, and his London accomplice Shah Rahman, 28, were followed by undercover detectives on November 28, 2010, observing Big Ben, Westminster Abbey, the London Eye and the Palace of Westminster.
The conspiracy involved nine defendants - the London duo, three from Cardiff and four from Stoke - but was stopped by undercover anti-terror police before firm dates could be set for attacks.
Mohammed Shahjahan, one of nine men who admitted various terror charges at Woolwich Crown Court
The terrorists met because of their membership of various hardcore Islamic groups and stayed in touch over the internet, through mobile phones and at specially arranged meetings - held in parks in a bid to make surveillance difficult.
The nine, all British nationals, were due to stand trial at Woolwich Crown Court but changed their pleas at the 11th hour.
Chowdhury, of Stanliff House, Tower Hamlets and Shah Rahman, 28, of St Bernard's Road, Newham, both London, admitted preparing for acts of terrorism by planning to plant an improvised explosive device (IED) in the toilets of the London Stock Exchange.
Abdul Miah faces sentencing next week
They admitted the crime after a Goodyear hearing was held to give them an indication of their maximum sentences.
The judge, Mr Justice Wilkie told Chowdhury he would receive 18-and-a-half years and Rahman, 17 years.
But the duo will only serve in the region of six years - because five are served on licence, prisoners only serve half their term as standard and they have already been behind bars for more than 12 months.
Brothers Gurukanth Desai, 30, of Albert Street, and Abdul Miah, 25, of Ninian Park Road, both Cardiff, also admitted the same count.
The quartet aimed to plant the bomb "with the obvious attendant risk but without any intention to cause death or even injury but with the intention to terrorise, damage property and to cause economic damage", said Christopher Blaxland QC, Chowdhury's barrister.
Three of the Stoke defendants admitted a lesser, specific charge - engaging in conduct for the preparation of terrorism between November 1 and December 21, 2010 - namely travelling to and attending operational meetings, fundraising for terrorist training, preparing to travel abroad and assisting others in travelling abroad.
Usman Khan, 20, of Persia Walk, Mohammed Shahjahan 27, of Burmarsh Walk and Nazam Hussain, 26, of Grove Street, all Stoke, admitted attending those operational meetings in Roath Park, Cardiff on November 7 and in a Newport country park on December 12.
Omar Latif, 28, of Neville Street, Cardiff, admitted attending the meetings with the intention of assisting others to prepare or commit acts of terrorism.
The fourth Stoke defendant, Mohibur Rahman, admitted possessing an article for a terrorist purpose on December 20 2010.
Rahman, 27, of North Road, admitted being in possession of two editions of the al Qaida magazine, Inspire, for terrorist purposes.