Absolute measures - Humphrey Hawksley

It begins with an SAS raid on a house in Khartoum which leaves the twins of an innocent neighbour orphaned. Saved from the orphanage by a Malaysian businessman, Samira and Yasin grow up in a world of wealth and privilege, but the seeds of hatred, sown when they were children, are about to reap a terrible harvest. When their home is plunged into violent chaos, Yasin knows the time has come for revenge. Suddenly the West is confronted by a terrorist with a plan so audacious that they are defenceless against it. Their only hope of stopping him lies with a man whose own life was also changed forever on that night in Khartoum, and with Yasin's twin sister Samira, who must make the most difficult choice of all.