In reply to purplemonkeyelephant:
It was the standard fatigue failure and split at one of the joints that all aluminium poles suffer from. Unfortunately the company had vanished and getting a spare section was difficult - 20 inch dac featherlite poles aren't common on european tents.
It also turned out that DAC have very slightly changed the inner radius of their 8.84mm featherlite pole sections so I had to get an ultra quasar pole and cut to length rather than just buy a single section. On the plus side it left me with lots of spares for the other poles.
The main reason I am considering letting it go is that I have a toddler and no real chance of going on the sort of trips that require a geodesic bomb shelter for the next few years. My camping is moving in the direction of tipis and civilised family sites with cake shops.