“A RIB is a rigid inflatable boat, and this has an engine at the rear which pushes the nose up and out of the water as it bounces along at a great speed. This was a good-sized one and I realised that it must have an antigrav component because it never sank in the water though the team of Neptunians got on with us. The marine engineer steering it took us out to the dive boat, a large – to our eyes – vessel over a mile offshore. We sat back and gripped the rope lacings along the sides and breathed in salt spray air, grinning foolishly at our friends and each other. The RIB engine was so noisy that we couldn’t really talk but we were relishing being right down at water level, streaking across the Thames estuary, heading for the most dangerous boat in the world.”