This article revisits British assessments on the Dardanelles during and after the Taba crisis in 1906. It is known that the assessments produced throughout 1906 were pessimistic. What is missing from the current historiography is the intelligence dimension. This paper fills this gap by arguing that the assessments were pessimistic because military and political assessors knew that the Dardanelles defences were strong. They knew this fact because British intelligence departments had compiled detailed and accurate information demonstrating that the Dardanelles defence system had been modernised and strengthened by the Ottomans over the preceding three decades.