Gordon Brown faced fresh questions tonight after it emerged that he discussed with Colonel Gaddafi detailed conditions for the Lockerbie bomber's return nearly six weeks ago, while senior Labour figures warned of an economic backlash from angry Americans "costing our country dear". Downing Street released the text of a cordial letter sent to the Libyan leader on the day that Abdulbaset al-Megrahi was released, asking that the event be kept low key because a "high-profile" ceremony would distress his victims and their families.