White Pasque-flower, one with double petals.
No interactions present.
There are several 'white' pasque flowers, and the easiest features to distinguish them are the leaves - stem leaves shortly petiolate or sessile; stem leaves like the basal leaves or not. However, the leaves are not easily visible here. P. vernalis usually has the underside of the outer petals flushed purplish, as in the iSpot featured below. P. alpina ssp alpina is also white or white flushed purple and is a calcicole. Yours look quite white, inside and out, so I think you may have P. alpina ssp alpina, or P. alba, a calcifuge. Maybe you have more photos or some notes to decide between them.
Much to my surprise I see that Pulatilla vernalis has reverted to Anemone vernalis as an accepted name.
Thanks for the comments JoC which highlight the problems. Sadly no more photos than these and I thought I had taken more of the underside in photo 2 but only got the hairiness of the plant. There is another possibility which is P. alpina subsp. millefoliata which seems to show more petals than the norm, like my i.d. With regards to leaves unfortunately the flowers were far more advanced than the leaves so no help there. May not resolve this one only to say that it is a Pasque-flower.
"Flowers more advanced than the leaves" could be a good clue. P. vernalis has evergreen leaves, so you would probably have noticed them. I find this site can be useful.
Thanks again for that comment. Florealpes is one of my most used sites but on this occasion led me to P.vernalis - I don't know why. However, I think you are correct and I will rename this Alpine Pasque-flower but I don't think it will be possible to i.d. the subspecies. May have to go back next year!! Val Cenis was a wonderful area for wildflowers and also Marmottes.
Lat/Lng: 45.2495, 6.9318