The political economy of the NHS and similar institutions

I have two questions about the NHS:

1. What are the political conditions under which the NHS functions at an arbitrarily “acceptable” level?
2. To what extent have these held in the UK over the last n years, where n represents an appropriately representative duration?

I now have a broader question about institutions:

3. If a healthcare system (or any institution, for that matter) requires favorable political conditions that can be perturbed by a fairly common occurrence, then how robust is that institution?