A jury on Friday was shown video footage of two London bombing suspects buying large quantities of hydrogen peroxide, the main ingredient for what prosecutors allege were homemade bombs that failed to detonate properly.
The men, Manfo Kwaku Asiedu and Muktar Said Ibrahim, are accused, along with four other men, of planning suicide bombings on the London transport system, using an explosive mixture of hydrogen peroxide and flour.
The purchase was made on July 5, 2005, just two days before the attacks on London transit in which 56 people died.
Prosecutors allege the men planned similar attacks for later that month.
The court heard that the peroxide order was made up of 13 boxes, each containing four four-liter bottles. The order was so large that the manufacturer had to make a new batch to meet it.
The pair were seen in the security video smiling, looking around and chatting as they waited to pick up the order.
Asiedu on Friday explained the large purchases as an efficient way to strip wallpaper.
Asiedu appeared relaxed and seemed to have "all his answers prepared" as he bought the entire stock of the strongest concentration of hydrogen peroxide from the Hairways store in London, Hairways director Christopher Diaper said.
Asiedu, 33; Ibrahim, 28; Ramzi Mohamed, 25; Yasin Omar, 26; Adel Yahya, 24; and Hussain Osman, 28, all deny charges of conspiracy to murder and conspiracy to cause explosions.
Prosecutors say the plot failed when four bombs failed to explode fully on subway carriages and a bus on July 21, 2005 — two weeks after four suicide bombers killed themselves and 52 other people in attacks on London's transport system.
The shop's manager, Giovanna Lanza, who said she served Asiedu and a companion, told the jury at the Central Criminal Court that they explained they were stripping wallpaper. She warned them that it could burn their skin.
"He said 'We wear protective clothing,'" Lanza recalled.
Diaper said he questioned Asiedu because of the unusual size of the purchase. "I wanted to be sure in my own mind that this was going to be used for the proper procedures," he told the court.
The prosecution says that Asiedu lost his nerve on the day of the planned attack and dumped his device in a park.
The bombs were made from a mixture of concentrated hydrogen peroxide and chapati flour, a recipe which the prosecution said could make a viable explosive. In every case, however, only the detonators fired properly, and the would-be bombers ran away.