For the last eight years a decrepit old oil tanker off the coast of Yemen has been like a ticking time bomb, threatening to unleash unprecedented disaster in the Red Sea. The 47 year old oil tanker, the FSO Safer, was fraying and decaying -- and filled with one million barrels of oil. For reference, this is about four times the amount that the Exonn Valdez spilled in 1989. The UN estimated that a spill from the SFO Safer would cause an ecological, environmental and humanitarian disaster across the Red Sea region, destroying pristine reefs, and imperling costal fishing communities in Yemen, Somalia, Djibouti, Eritrea and beyond. It would take 25 years for fish stocks to replenish. The cleanup alone would cost $20 billion.

But today's episode is about how that disaster was averted. On Friday, August 11th the United Nations announced that the FSO Safer's 1 million barrels of oil had been offloaded. This was the culmination of a massive political, diplomatic and logistical undertaking and my guest is the person who was at the center of it all, the UN's top official in Yemen David Gressly.

David Gressly is an Assistant UN Secretary General, with whom I spoke from Aden just hours after the last oil had been pumped out of the FSO Safer. We kick off discussing the circumstances in which the oil became trapped in the old vessel, which is very much part of the story of Yemen's civil war. But this is a good news story of a crisis averted.