A friend of the alleged July 21 London terror plotters has told a court how he helped to collect the main ingredient for their rucksack bombs, but only because he thought it would be used for painting and decorating.

Matthew Dixon told Woolwich Crown Court that he believed he was driving Manfo Kwaku Asiedu, one of the alleged bombers, to a hairdressing wholesalers in North London to pick up supplies of bleach for "stripping walls".

In fact, the prosecution claims, Mr Asiedu wanted to use the 16 litres of hydrogen peroxide - purchased from Hairways in Tottenham on May 19, 2005 - to develop home-made bombs to explode on London's public transport system.

Before doing their shopping, Mr Dixon had said he was initially reluctant to help because he was busy with his masters degree, but Mr Asiedu had insisted because Mr Dixon was the only one with a car.

Mr Asiedu, 33, of no fixed address, is one of six men accused of hatching an extremist plot to carry out a series of murderous suicide bombings on the London public transport system on July 21 2005, two weeks after the July 7 bombings killed dozens in the capital. All five bombers allegedly went to their targets, but their explosives failed to detonate, and they attempted to flee.

The other defendants are Muktar Said Ibrahim, 28, of Stoke Newington, North London; Ramzi Mohammed, 25, from North Kensington, West London; Yassin Omar, 26, from New Southgate, North London; Hussain Osman, 28, of no fixed address; and Adel Yahya, 24, of High Road, Tottenham, North London.

"He (Mr Asiedu) said I was the only person he knew with a car," Mr Dixon told the court.

"I was quite reluctant - I was busy at the time. I was also worried about the damage it might do to the car. I did not know the details of what he was carrying - I did not know if it was going to get the seats dirty."

Asked if he knew at that time of the potential use of peroxide in explosives, Mr Dixon replied: "Of course not, no," adding: "This is months before any attacks in London. I knew he (Mr Asiedu) was a painter and decorator by trade. It seemed perfectly feasible that he needed to pick up supplies. I had no reason to doubt what they were going to be used for."

Despite getting the haul of 16 litres from the Tottenham store, Mr Dixon told the court that Mr Asiedu had then insisted that they went to another shop as he still did not have enough.

He said they drove to Sally's hairdressers in Finchley where Mr Asiedu bought more bottles, which they carried to the home of another alleged bomber, Yassin Omar, who lived in Curtis House, New Southgate, north London, the home labelled by the prosecution as the conspirators' "bomb factory".

All six men deny charges of conspiracy to murder and conspiracy to cause explosions likely to endanger life.

The trial continues.