For the three days on Mont Blanc itself, the guide: client ratio is 1: 2, which means that if one climber needs to descend for some reason (e.g. because of altitude sickness), the other climber might need to go down as well.

In practice this very seldom happens, firstly because we only run 6 day courses so altitude problems are rare, secondly because we suggest (but don't insist) climbing partners of similar speeds climb together, and thirdly because all our teams are in radio contact on the mountain so we can change things around if necessary (e.g. a fast team descending from the summit could pick up an exhausted climber from a still ascending slower team and take him down to the nearest hut, where he could warm up / drink some tea until his original team came to collect him).

Ideally each climber would have their own guide, but this would hugely increase the course price and we feel 1 guide: 2 climbers on Mont Blanc to be the best compromise. We have nearly always in the past managed to avoid the awful disappointment of an otherwise fit climber being required to descend because his partner can't continue, but however unlikely it remains a possibility, and it is as well to be aware of this.