The wind had dropped the night before, but the sea was still running pretty heavy, especially for a boat like the Lucette. The waves were about head height and in a small boat there was a real risk of going over the side. In the distance a shape in the sea moved towards the yacht.

On board, the Robertson family were 200 miles west of Galapagos and two days into a 40-day leg to the Marquesas Islands in French Polynesia on their round-the-world voyage. Some of the family were sleeping below deck, having kept watch through the night. The morning coffee was brewing on the stove and the family were settling into their normal daily routine. The events that took place in the next few seconds would change their lives forever.

Douglas Robertson, who was 18 at the time, was in the cockpit with his younger brother Sandy when he saw it: the triangular fin of a killer whale. “I pulled a fishing line in and there was a big squid on the end of it, you know, and I said to my brother ‘There’ll be some big fish around here’,” he recalls. “Because where there’s squid there's whales.”

And then came the impacts. Three in all, in quick succession. Their 43ft (13m) wooden schooner, was lifted into the air, the occupants thrown off their feet. The crack was so loud it could only mean the keel, a single piece of wood that runs the entire length of the bottom of the boat, 3ft (0.9m) deep and 1ft (0.3m) wide, had snapped.

“I thought we must have gone aground,” says Douglas, who is now 65. “We must have hit the bottom somehow, even though we were in deep sea, because I couldn't think of another explanation for what happened. I looked down the hatches and said, ‘Dad, are you okay?’ And he was already up to his ankles in water.”