Extra police were on duty as around 20 members of the English Defence League watched proceedings below.
Earlier, they had demonstrated outside the central London court saying they objected to the "Islamification of Britain".
Nine men appeared in court by prison videolink accused of a plot to target landmark sites such as the Stock Exchange, the Houses of Parliament and the US Embassy.
They are alleged to have also targeted political and religious figures in the plot in the run-up to Christmas.
The defendants were remanded to another hearing on February 25.
Mr Justice Calvert-Smith said their trial would not take place until at least January next year.
The venue is likely to be Woolwich Crown Court but he will listen to representations from lawyers about alternative courts.
The suspects from Cardiff, London and Stoke-on-Trent, were arrested following a series of dawn raids by counter-terrorism officers on December 21.
They are charged with conspiring to cause explosions likely to endanger life or damage property between November 6 and December 21.
A further charge alleges they were preparing for acts of terrorism between the same dates.
This was said to be by agreeing potential targets, carrying out reconnaissance, attending meetings, igniting and testing incendiary material and researching and discussing materials and methods.
The defendants from Cardiff were Gurukanth Desai, 29, of Albert Street, Omar Sharif Latif, 27, of Neville Street and Abdul Malik Miah, 24, of Ninian Park Road.
The defendants from London are Mohammed Moksudur Rahman Chowdhury, 20, of Stanliff House, Tower Hamlets and Shah Mohammed Lutfar Rahman, 28, of St Bernard's Road, Newham, both east London.
The defendants from Stoke-on-Trent are Nazam Hussain, 25, of Grove Street; Usman Khan, 19, of Persia Walk; Mohibur Rahman, 26, of North Road and Abdul Mohammed Shahjahan, 26, of Burmarsh Walk.