Book excerpt: Trust is the Coin of the Realm shines a rare light into the labyrinth of Afghanistan's 'money men' and their influential informal economy that links the Islamic world. Hawala is the ancient financial system that predates Muhammad, and provides a vital key to engaging with many of the world's traditional cultures. Stereotyped as 'built for terrorism' and a dangerous pipeline for dirty money in the wake of 9/11, Thompson reveals it to be indispensable to the work and reach of humanitarians, donors, family members, and the business community. Outsiders striving to build states and peace in crisis countries will find this book invaluable for earning the trust that is essential if their efforts are to make a lasting difference.