There is a technique of detective story writing where the solution is made clear at the outset, though in a disguised form. Landscape with dead dons by Robert Robinson, the well-known broadcaster is probably the most perfect example of the technique, the murderer's name hidden in the first paragraph at the start of the book which are some lines of a poem by Chaucer, or are they?
One of the best Lockerbie books John Ashton and Ian Ferguson's Cover-up of convenience, may be an example of this technique in action. Chapter 1 begins:
"No one thought to ask how they had got there so quickly. The middle-aged Americans wandering around Lockerbie town centre were clearly not bewildered tourists. Dressed in cream trench-coats the men exuded an air of purpose which could only mean they were there on official business. With hindsight their presence was the first public clue that the bombing of Pan Am 103 was no straightforward act of terrorism(.)"
I think of them as being two, though the authors do not say that. There may have been more but not a single man.
In my theory, which Ferguson and Ashton do not develop - they use a rather different fact base from me - for instance they mention neither Marquise, the FBI lead investigator, nor Charles, who led the AAIB team, according to the index - a theory of criminal responsibility for the atrocity from the outset that blames US government agencies.
If there were two, I call them CIA men and their names were most probably Hantzauman and Cattermole, both of which are pseudonyms. Cattermole was the more senior, Hantzauman an experienced operative.
In my scenario, entirely hypothetical, Hantzauman may have detonated the second explosive in the CRAF hold of the aircraft on the package or insurance bomb using a pager detonator. The quietly spoken Cattermole may have been there to begin to begin the process of controlling the investigation, so that it did not reveal material inimical to the Agency or the United States. It would be a long process of fakery and fabrication that would lead to the jailing of Libyan citizen over 12 years later.
They then presented themselves in Lockerbie as early as they decently dare, and certainly by 9pm. The fires would still have been raging in Sherwood Crescent. They then may have liaised with US diplomatic staff and the US consul-general from Edinburgh was early on the scene, the US ambassador to Britain arriving on the first aircraft into Carlisle, sometime before midnight together with other CIA staff.