True Colours by Stephen Leather

The Russian oligarchs are the world's new elite. They treat the world as their plaything, traveling without borders and living lives of unimaginable luxury without fear or restraint.

But when an assassin starts killing off some of the world's richest men, an oligarch with friends in high places seeks the protection of MI5. And Spider Shepherd is placed in the firing line.

But while Shepherd has to save the life of a man he neither likes nor respects, he has to deal with a face from his past. The Taliban sniper who put a bullet in his shoulder turns up alive and well and living in London.

And Shepherd is in no mood to forgive or forget.