On Sunday 20 May 2012 Abdelbaset al-Megrahi died of cancer aged 60. He is the only person to have been convicted for the bombing of Pan Am flight 103 over the Scottish town of Lockerbie on 21 December 1988. The attack, which killed 270 people in the plane and on the ground, remains the deadliest terrorist incident ever to have taken place on British soil. But what is the legacy of the Lockerbie bombing and what effect will Megrahi's death now have?