Published pre 2006, probably UK author.

In the prologue, a UK expat family is somewhere in Africa, and the parents are suddenly killed, I think in a helicopter crash that turns out not to be an accident.  The children sounded interesting, but they aren’t very relevant to the rest of the story.

The rest of the story focuses on a single male protagonist, in his 30s or 40s, probably the brother of the woman who was killed.  He is drawn into some international conspiracy, is at some physical peril, and solves things.

I thought it was by Sam Llewellyn but I can’t find it on his website.  It has that kind of feel – like Sam Llewellyn or Dick Francis or the Canadian Jon Evans, a likeable but lonely amateur accidentally falling into a crime network.

In the mass market paperback edition I read in Canada in the late 1990s or early 2000s, the cover might have had a silhouette of a tree on a yellowish sky, and the title might have been Under the (some variety of exotic) Tree.