What should have been one of the great achievements of Irish climbing turned, in a few hours, to possibly the worst disaster ever to take place on K2, the world's second-highest mountain.

Of the 17 that reached the summit, between eight and 10, including Ger McDonnell, are now thought to be dead.

Ger's family, his friends, and all of us are trying to come to terms with his death and that of the other team members.

However, all of us who love climbing are fully aware of the dangers involved. We know that one in two people who attempt to climb K2 die.

But we, as climbers, take to expeditions with a great love and passion for what we do, despite the obvious dangers that may be around the corner.

All climbers know that once they ascend to more than 8,000m, they are entering a place called 'deathzone'. We are fully aware, as Ger was, of the risks we take in going to such places. Ger, more than anyone, would have known the risks.

But, on K2, Ger made all the right decisions. He and the others were just victims of a horrific fluke of nature. He was one of the strongest and safest climbers I knew.

I have been on over 62 expeditions and Ger has been on four of them with me. He was on the Everest expedition with us in 2003 when we followed the original route as pioneered by Hillary.

He was a team leader, with fellow climber Rolf Bae, who also lost his life this weekend, of an Antarctic expedition which honoured Irish polar heroes like Shackleton, Crean, Keohane and the McCarthy brothers.

K2 looked like a textbook summit, with perfect conditions. But, as the group descended, a 'serac' sheet of ice split off and cascaded down the mountain, wiping three climbers out, and leaving nine climbers above bottlenecked in deathzone.

Our hopes were briefly raised when a lone climber in an orange jacket was spotted descending the mountain on the Cessan route. We prayed it was Ger. But it was another climber, Wilco, who had thankfully returned safely.

There is a slim chance, of only 1pc, that they may still be found but we have to accept that, on the law of averages, they are now lost to K2.

The weekend's tragedy looks like it will be the worst fatality ever on K2, surpassing a disaster in 1986 when eight people were killed on the mountain. This time, it looks like it may be as much as 10.

There will be no-one else sent up to look for them now because the risks are just too great. We accept, as Ger's family do, that he will not be coming down from that mountain.

Ger is rightly being feted as a hero for being the first Irishman to climb K2. It is, as President McAleese said, truly heartbreaking that he is now gone.

The family are in severe shock, as we all are, and are still trying to comprehend what happened on K2 after the emotional rollercoaster of the last few days.

We have experienced the highest emotional peak and delved the lowest trough in these last few days.

On Friday, we were up there with Ger. Everybody was ecstatic when the news filtered through that the team had reached the summit. All the efforts seemed to have paid off, and it looked like they had completed one of the great climbing achievements. However, as morning broke over K2 on Saturday, the disaster began to unfold.

But Ger's family can console themselves with the fact that Ger lived his life to the full and was a man very much full of the joys of this life. He was gregarious and happy go lucky and the various expeditions I undertook with Ger forged strong bonds between us.

Such bonds are essential on those dangerous journeys -- in fact, they are the very strength of the expedition itself.

On all his expeditions, Ger was known as the life and soul of every trip, renowned for his unlimited energy and legendary wit. He would sing Irish songs as we travelled, and endeavoured to bring a bodhran with him on every expedition and play it atop the summit. We don't yet know if he managed to put it to use on K2.

The shock to our office is that two people I have been on expeditions with are now dead. Rolf Bae, one of the world's top explorers, has also been taken from us.

Both he and Ger, one of Ireland's great climbers and a true gentleman, are now gone. At times like this, it's hard to take in the magnitude of such loss.

Pat Falvey is an Irish adventurer who has completed over 62 expeditions around the world, including the Seven Summits, Everest and the South Pole.

- Pat Falvey