"I was the only black person there in a class which was completely white," said Bowen, who found hearing the racist language in the book repeated in lessons "really awkward" and "confusing".

Whatever their reasons for not responding, as the Saudis claim, to the repeated warnings about his extremism, he was clearly a danger to his adopted host country.

A pothole is a hole in a road surface caused by factors such as repeated traffic impact and water damage.

The prosecution case at Megrahi's trial, which will be repeated in Washington, was that Libyan intelligence agents smuggled the bomb onto a flight from Malta in an unaccompanied suitcase.

In small concentrations, the risks from one-time use are minimal, but increase with repeated exposure over time.