An Old Bailey jury has been shown video footage of a man entering a storage unit linked to an alleged bomb plot.
The police footage shows Omar Khyam entering a storage depot in west London where a 600kg bag of fertiliser was stored, in March 2004, jurors heard.
It shows Mr Khyam in the unit for a few minutes inspecting the bag, they heard.
Prosecutors say the fertiliser was to be made into explosives but Mr Khyam and six other defendants in the case deny conspiring to cause explosions.
The trial has been running since March but this is the first time the jury has been shown pictures of what the prosecution said was one of the defendants with the fertiliser.
During the two-and-a-half minute-long footage, Mr Khyam appears to walk into the room, peer into the bag and have a look at the side of it.
He bends to mark the point where the powder came up to in the bag, fearing it might be tampered with, the prosecution said.
Seven men all deny plotting to cause explosions
The court has been told police and secret services had been watching Mr Khyam and others suspected of being part of a British al-Qaeda cell.
Unknown to Mr Khyam, they had already replaced the volatile fertiliser with a safe substance, jurors heard.
Workers at Access Storage in Hanwell, west London, where the fertiliser was stored, had alerted police after becoming suspicious.
Mr Khyam was tracked by MI5 surveillance and anti-terrorist branch for six weeks.
All the defendants were arrested on 30 March 2004.
Mr Akbar, 22, Mr Khyam, 24, and his brother Shujah Mahmood, 19, and Waheed Mahmood, 34, all of Crawley, West Sussex, Salahuddin Amin, 31, of Luton, Beds, Anthony Garcia, 23, of Ilford, east London, and Nabeel Hussain, 21, of Horley, Surrey, are accused of conspiring to cause explosions likely to endanger life between 1 January, 2003 and 31 March, 2004.
Mr Khyam, Mr Garcia and Mr Hussain also deny a charge under the Terrorism Act of possessing 600kg (1,300lb) of ammonium nitrate fertiliser for terrorism.
Mr Khyam and Shujah Mahmood further deny possessing aluminium powder for terrorism.