John Laverie may find it illuminating to peruse John Ashton's book Megrahi: You Are My Jury (Libya's Gulag: questions linger, Letters, June 19). It contains a number of references to Moussa Koussa, former head of Libyan intelligence. Ashton states that Koussa was debriefed at an MI6 safe house in the spring of 2011 and shortly after was interviewed about Lockerbie by the Scottish police. He was then allowed to leave the country and his assets were unfrozen. Ashton suggests that one obvious reason for Koussa not being arrested was that the UK Government was well aware that neither he nor Gaddafi had anything to do with Lockerbie. A less obvious explanation was that Koussa was a long-time MI6 asset. On March 30, 2011, the Daily Telegraph stated: "As head of Libyan external intelligence, Mr Koussa was an MI6 asset for almost two decades."

In his book, John Ashton recounts the experience of Martin Cadman who lost his son Bill in the Lockerbie bombing. In February 1990, Mr Cadman was invited to the US embassy in London to meet the members of a presidential commission established to examine aviation security policy with particular reference to Lockerbie. At the end of the meeting Mr Cadman was taken aside by one of the commission's seven members who said to him: "Your government and ours know exactly what happened [regarding Lockerbie] but they are never going to tell."

Alan Woodcock

Dundee

I read John S Laverie's letter with particular interest as I had just finished Kenny MacAskill's book, The Lockerbie Bombing – The Search For Justice (Libya's gulag: question linger, Letters, June 19). MacAskill, who was Justice Secretary and responsible for making the decision to release Megrahi on compassionate grounds, brings clarity to a subject muddied by conspiracy theories – he covers the issues of rendition, the involvement of MI6 and the role of Moussa Koussa, and I thoroughly recommend the book to Mr Laverie and all those interested in a clear-headed analysis of the Lockerbie atrocity.

Ian D Cochrane

Wigtown