The way azalea roots grow, spread out, close to the surface, under a thick covering of mulch (like ground up leaves), I would say that plant will not live a significantly long time in a small pot like that. I am hoping that your plan for it in the pot is just for a little while. But your question is about pruning - azaleas can be completely butchered and come back as nicely as you can imagine. I remember getting a few azaleas from a flower bed my sister was eliminating from our family home. They had been in place about 40 years, and they were massive. I could not manage the whole plants, so I cut everything back to no more than a foot. These things not only came back, but they also bloomed the following year. They were beautiful and much better shaped than their old 6 to 8 foot spread. I would cut that one back to about a foot, which would make it much nicer, bushier and full. But that thing needs to be in the ground with lots of organic matter - and azaleas do not need a great deal of sunlight. I grew up in a yard that rivaled the Azalea Gardens in Norfolk, VA, and 90% of it was in complete shade of large trees.

Many thanks, greatly appreciated

One of the problems with both the original post and the reply from drmbear is the use of the term "azalea". The photograph seems to show a deciduous variety, perhaps one of the native Americans or one of the many hybrids. If that is the case, the growth pattern with leaves in whorls at the end of the branches is entirely normal. It can probably be made bushier by cutting back some of the longer branches, but it will need a sunny location to grow well. drmbear's reply would apply to evergreen type azaleas which do grow and bloom in shady locations and respond extremely well to very extensive pruning. It is possible that the photograph shows an evergreen azalea that has grown very leggy over time, but it is impossible to give sound advice about pruning without knowing at least what type azalea this is.

No matter what type, deciduous or evergreen, I'd prune that one for it's branching pattern rather than start over and go for a dense ball look. Maybe an Asian look with 3 or 5 trunks. Most of the deciduous azaleas grow a little on the lanky side anyway.

Mike

Even the deciduous varieties we would cut back to about two feet every 5 to 7 years. Those things would sprawl out to 6 or 7 feet tall and just as wide. We had a long strip along the driveway of these large flowered lavender color that were amazing.