Wind damage is a noted problem with Nothofagus pumila grown in Britain, which grows too effusively in most of Britain's relatively low wind conditions, and then suffers wind damage when the wind does blow. N pumila is a good timber tree, but needs to be grown somewhere windy to avoid this overgrowth. I hadn't known it as an issue with N antarctica which is smaller and not interesting for timber. My tree does not seem to be unusually effusive in comparison with Patagonian examples grown in relatively sheltered locations, such as within woods, although it is clearly effusive in comparison with those grown somewhere with a serious blast.

The splits in the trunk are vertical. The weakened roots are close alongside a low beech hedge, so might be weaker because of competition on that side, though the beech hedge is kept very low so I would have thought that a sizable tree would have been able to get its roots really deep after 12 years in the ground, and well under the hedge. I really can't do any digging beacuse of the nearby plants.

Where we are on the Chiltern plateau, the subsurface clay is pretty deep over the underlying chalk (with a light loam topsoil) - in fact the chalk is so deep I don't know how deep it is - when we had a new garage put up the foundation diggings didn't expose chalk. There's a place in a similar plateau location near Berkhamsted where they have dug a big hole to show you the soil horizons, and they don't get down to the chalk.

Generally speaking I find that newly planted trees grow slowly to start with and are drought prone for a few years while they are in the loam. Then they get their roots into the subsurface clay, and start to grow quicker, and don't suffer from drought any more. This tree has been like that, indeed it seemed to get its roots deep most quickly than some.

I think based on what you say I'll chop the tree off about 6 ft above ground level, and see if it rights itself. If not, I'll cut it lower.