What is (if there is one) the equivalent of the tenure-track phase in Europe? In the US, tenure-track (TT) positions seem a common and natural step in the progression towards an academic career and quite "stable" state-wise in terms of what one might expect from them, in that if nothing goes too wrongly, after the fixed X years in a TT position one can reasonably expect to get tenure (I've heard of  horror stories of denied tenure from certain R1 universities, but I'm more concerned about the generic case here).

Now, I'm in the early stages of my academic career (I'm soon to start my first postdoc) and, more relevantly for the purposes of this question, I'm based in Europe and, unless I have absolutely no other options, I intend to remain in Europe in the future. My understanding of what the "natural" steps to take after the postdoc phase in Europe is, admittedly, pretty muddy and quite scattered.

My question(s) is (are):


  
    Is there an equivalent (step-wise in the progression towards an academic career) in Europe of the tenure-track positions in the US? If so, is this equivalent step "stable" country-wise, or does it change considerably depending on the country? More generally, what is the "natural" progression in Europe after the postdoc phase?
  


Sorry for the many questions, but most of the advice I usually find is very US-centric.

EDIT: To make the question a bit more specific, I'm particularly interested in France, UK, Italy, and Germany. Also, I'm trying to pursue an academic career in mathematics, so I'm also interested in those aspects specific to the discipline, if there are any such.
In the UK there are four levels of permanent academic employment: lecturer, senior lecturer, reader, professor. These four positions between them are roughly equivalent to the three US positions of assistant professor, associate professor, professor. These days lecturer is often a probationary position for the first few years, but higher positions are permanent. Promotion to senior lecturer does not follow automatically upon being confirmed as a permanent member of staff. Apart from this practice of probationary appointment there is no formal tenure system. In my experience (which is limited to mathematics departments) it is quite unusual for probationary appointments to not become permanent.

In my understanding, not very long ago senior lecturer and reader were seen as roughly equivalent, but senior lecturer was seen as more heavily emphasising teaching and administration whereas reader was seen as a position which more strongly emphasised research. However, there is a developing tendency to see the two positions as having essentially the same nature, with reader simply being more senior.

Some British universities are in the process of adopting the three-tiered U.S. nomenclature, but such universities remain a minority at present.