A much publicized incident last week on the Grandes Jorasses, which could be followed in almost real time on the Internet, ended in tragedy, when French guide Olivier Sourzac and his client Charlotte Demetz perished in a ferocious storm.
The facts, as far as can be ascertained, are as follows, though are by no means guaranteed as exact.
On Monday 1st November Italian and French meteos were forecasting a large tropical-like storm that would move north east across the Mediterranean and strike North Western Italy and southern France on the Thursday.
The timing was correct with some of the heaviest rainfall for 17 years, nearly a full flood alert in Turin, and six people drowned by flash floods in Genoa.
On the Tuesday, with wonderful clear blue sky over Courmayeur on the south side of the Mont Blanc Massif, Sourzac and Demetz moved up to the Leschaux Hut beneath the North Face of the Grandes Jorasses.
Their plan was to climb the Shroud, traverse the summit and descend to Italy.
Conditions on the Shroud had reportedly been excellent, and the pair took minimal equipment for a light and fast ascent, no doubt confident they could complete most of the descent, if not reach the Boccalatte Hut, by Wednesday night.
Sourzac was a gifted climber and instructor at ENSA (Ecole Nationale de Ski et d'Alpinisme in Chamonix) and Demetz was a regular client. A good rock climber, Demetz was known to have done the Central Pillar of Frêney.
However, for reasons unknown the ascent of the Shroud took a very long time, the two exiting not by the standard line to the left but via the three-pitch direct finish. They bivouacked on the crest of the Hirondelles Ridge at an altitude thought to be between 3,800-3,900m.
Despite having only a small bivouac bag and space blanket, they appear to have been fine next morning but took until 11:00am to reach the summit of Pointe Walker (4,208m), where Sourzac telephoned to say his client was in trouble and they needed a rescue urgently.
At around this time a classic föhn storm hit the mountain, producing huge winds and the onset of snowfall. The winds would be so strong that the Mont Blanc Tunnel had to be closed to traffic, because of the huge difference in atmospheric pressure between the two entrances.
Rather follow the popular descent via Pointe Whymper and the Rocher Whymper, the two decided to lose height by going straight down the old Normal Route towards the Plateau.
However, they only reached 4,050m before bivouacking again, out in the open on steep ground at the top of the rocky rib leading down to the eastern end of the Plateau, below a boulder that would give some protection from the snow but not the wind.
At around midday on Friday Sourzac telephoned, inferring Demetz was in a poor condition and they would have to move, out onto the slope to the west where they might be able to dig in by the serac. Then the phone died.
At this stage it was reported that they were on the Rocher Whymper and would dig in close by.
Meanwhile the PGHM (Peloton de Gendarmerie de Haute Montagne) in France had been unable to fly towards the Jorasses due to the wind and poor visibility, and asked the Val d'Aosta team to try from Italy. They also failed. Noted alpinist Bruno Sourzac, brother of the trapped climber, and several friends reached the Boccalatte Hut but were then unable to make much progress above due to zero visibility, strong winds and driving snow.
In the ensuing days more attempts were made on foot and by both the PGHM and Val d'Aosta helicopters to no avail, but on Sunday 6ththe PGHM, with impressive flying skill, managed to lower two people onto the summit ridge.
They were only able to remain a couple of minutes but left survival gear and reported over a metre of fresh snow on the slopes.
Tuesday's weather was probably worse but the Italians were able to fly over the South Face and again were unable to spot the whereabouts of the stranded climbers.
But on Wednesday the wind was dropping and in the last minute of a 40-minute reconnaissance, with the helicopter close to the wall, the PGHM team spotted the bright red windsuit known to be worn by Demetz. It's possible that the down-draft from the rotor blades may have blown off enough surface snow for this to become visible.
When the Italian rescuers were dropped at the site, they found the climbers sitting on their ropes, belayed by a peg and covered in snow. They hadn't moved from their Thursday night bivouac. An initial guesstimate is that they most likely succumbed during Friday night.
One positive thing to emerge from this tragic outcome was the cooperation, coordination and sheer bravery of both teams, which made outstanding efforts to save the climbers in extremely hostile conditions.
Thanks to Luca Signorelli for full details and complete cooperation on this report