At 0830 Tuesday 14 August 1979, aged 17, five minutes changed my life. Five minutes that, despite the stress of the previous six hours, would encapsulate the most extreme emotional highs and lows that I would ever experience. Five minutes that would be stretched to the longest minutes of the night and culminate in the most important decision I would ever make to this day – a decision that would need to be made in the most testing conditions. And a decision that I would feel forced to justify three decades later.

During what turned out to be the wildest and most destructive night in yacht racing history, our six-man crew aboard Grimalkin, a 30ft Nicholson half tonner, saw conditions deteriorate rapidly as we headed out across the Celtic Sea on our way to the Fastnet Rock.

Aboard were my father, David Sheahan, Gerry Winks, Mike Doyle, Nick Ward, Dave Wheeler and myself. All had experience of offshore racing, all had raced together aboard Grimalkin for most of the season through a variety of what we thought were testing conditions, yet none of us had any idea how far we would be pressed during the next few hours.

The first knockdown was a shock to the system, a one-off, an extreme incident that, like lightning striking twice, was impossible to imagine happening again. But when it did, time after time, it was clear that our focus had changed from racing to survival.

As we careered down the perilously steep face of a yet another mountainous wave it was clear this was going to be a big one – at best a terrifying white knuckle ride, at worst the end of our night. Within a few seconds our boat speed leapt from a lethargic amble in the trough of the wave to a thundering plane as the wave pitched us head first into the invisible trough 40-60ft below.

Running down what felt like a vertical wave under bare poles in the dark while trailing multiple warps, there was nothing we could do to slow down. As the log wound itself up like the rev counter on an engine that has just been floored, a pair of huge white bow waves arced out from each side, providing a V-shaped wall of water ahead.

The continual howl of the storm was deafening, but the rumble and hiss generated by this outrageous burst of speed rose above the background. A soul-chilling surge of fear swept through all of us as we heard the terrifying sound of a breaking wave 40ft above us.

In just a few seconds the 10ft high foaming crest was bearing down on us from behind like an avalanche. We dared not look back. There was no escape.

As time slowed down before the inevitable crash, the most terrifying aspect of our predicament was the realisation that we had no more options. There was simply nowhere to go.

Any attempt to steer along the face of the wave was futile and would have meant a knockdown and tonnes of foaming water cascading onto the boat.

Having been knocked down repeatedly and the crew thrown into the water, we’d already been there several times during the night.

Pitchpoled

We braced ourselves for the pooping of our lives, but a split second before the onslaught from astern, the bow disappeared as we nosedived into a wall of water in front. No one had seen that coming, not that it would have done any good if they had.

As the bow submarined into this secondary wave, Grimalkin’s stern rose until it arced over the bow and stood us on our nose. As we approached the vertical, crew were thrown against the back of the coachroof or out of the boat altogether. A split second later and we were hit from astern by the breaking wave and we pitchpoled.

Solid water and bubbles rushed past my face, my limbs streamed out as I was towed underwater like a mackerel spinner by my harness line. I had no idea which way was up, where the boat was, or what would happen next. Helpless, overpowered and overwhelmed, when your predicament gets to this stage your mind goes into an alien state where fear is replaced with resignation. But, as I was to discover three hours later, this clearly wasn’t my time yet.

Seconds later I broke the surface, trailing alongside the boat, spluttering, thrashing around and desperate to get hold of anything connected to the boat. Although she had righted herself, Grimalkin was now starting to accelerate down the face of another wave.

I don’t really know what happened next other than somehow I managed to get back aboard. As I scrambled back on deck, I could hear shouting, but in the dark, the noise and the drama of the conditions it was impossible to work out who was saying what.

As I tried to make sense of the situation I looked aft to see a pair of hands clutching one of the vertical legs of the pushpit. It was Dave Wheeler hanging on, struggling to keep his head above the quarter wave. As the stern pitched and heaved, somehow we pulled him back aboard.

I sat there and looked at him and for a reason I still don’t understand, ran my hand down his harness line to find his carbine hook floating free, detached from the boat. Both of us went numb with shock.

Until this moment, running with the seas had been slightly more comfortable, safer even, than trying to reach across them or lie ahull where we felt like a sitting duck waiting for yet another breaking crest to roll us on our side, sometimes through 360°.

Sailing downhill reduced the apparent windspeed, reduced heeling and provided a degree of manoeuvrability that allowed us to dodge the terrifying breaking crests. The trouble was that at speed and with waves coming from all directions – now the breeze had swung through 90° – the potential for a major pile up was greatly increased.

The reality was that until now we had simply been lucky, most of the breakers had rolled past us on either side – just. On this point of sail there was no skill in avoiding the waves, we were simply playing a game of Russian roulette. And when the bullet and the barrel lined up, the waves that struck us broadside had simply laid us flat or rolled us, ejecting the crew into the sea.

Running out of options

That was frightening and risky enough, but the pitchpole that we had just experienced was all the more distressing as it drove home the unpleasant truth that we were fast running out of options. What else could we try? How much more could we take? How much more could our boat withstand and how much more water below decks would it take to see her start to sink?

As we took knock after knock, thinking beyond the next 60 seconds seemed impossible. Tired, cold and hypothermic, just responding to our surroundings second by second was the best our six-man crew could achieve. Our ability to make rational decisions was being impaired rapidly.

Even the simplest things were becoming difficult. I remember that, despite recognising the various components of zip on my oilskin jacket, I just couldn’t work out how to do it up.

But, over the course of the next few hours, life was about to become far more taxing and present the most serious dilemma I have ever experienced.