A British terror cell was planning multiple bomb attacks in the UK on the same day, the Old Bailey has heard.
Seven men deny charges including conspiracy to cause explosions
Potential targets were stations, pubs and nightclubs, "supergrass" Mohammed Babar told the jury.
Babar is giving evidence against seven men who deny charges including conspiracy to cause explosions.
He claimed the plan was outlined in 2003 after one defendant Omar Khyam, 24, of Crawley, West Sussex, held a meeting with a leading al-Qaeda figure.
"He wanted to do multiple bombings at the same time," Babar told the court.
"Either simultaneous, or one after the other on the same day."
Babar told the court Mr Khyam had wanted to discuss "what they were planning in the UK" with al-Qaeda.
The trial also heard an alleged co-conspirator, currently awaiting trial in Canada, had been working on fitting a model plane with explosives.
Babar told the court Mr Khyam met Abu Munthir, the deputy of Abdul Hadi - described by the prosecution as the number three in al-Qaeda - in the northern tribal area of Pakistan near Kohat.
On his return, he said that Munthir wanted to see "everyone involved" in the plot, Babar alleged.
Babar, 31, has claimed he first met some of the defendants at a training camp in Pakistan.
The Pakistani-born American citizen has pleaded guilty in the US to terror offences, but has been given immunity from prosecution in the UK.
Babar said "differences" developed between the alleged plotters and he went to London to "clear everything up" in January 2004.
The next month, however, while back in the US, he heard about the arrest of the defendants on the news. He was held by the FBI himself in April.
Waheed Mahmood, 34, Mr Amin, Jawad Akbar, 22, Mr Khyam and his brother Shujah Mahmood, 19, all of Crawley, West Sussex, Anthony Garcia - also known as Rahman Adam - 23, of Ilford, east London, and Nabeel Hussain, 20, of Horley, Surrey, deny conspiring to cause explosions.
Mr Khyam, Mr Garcia and Mr Hussain deny possessing ammonium nitrate fertiliser.
Mr Khyam and Shujah Mahmood deny possessing aluminium powder.
The trial continues.