Massacre at Brewer Lane

Set in London,1990, the killing of five people in The Sisters' Basement nightclub gave DCI Bill Harrigan, in his role as Special Agent of the United Nations International Investigation Agency (UNIIA) with one of his most difficult cases yet. Why was the investigation given to UNIIA and not the local Police? Who was the target? The drugs dealer and International Arms Dealer or one of the other three? Why was the UK Government's Joint Intelligence Agency determined to remove UNIIA from the case at any cost?