cordyline - dry rot?

Oh NIgel - sorry to hear your Cordyline is poorly. We bought two of these a couple of years ago, about 12" tall. They're now about 5' tall. They grow so quickly don't they? We also have a Canary Island Palm which has the same symptoms as your Cordy, we believe it got too wet as new fronds were being formed. It looks like a straggly mess now. We're just going to leave it in and hope it makes a recovery. Sorry I can't specifically help with your problem though.

seams it was pot bound , i decided to put it in the ground but ended up cutting the pot in half to get it out ,but it is definitely looks alot happyer now.

they can get to much water when the weather warms up if they are not in a well drained soil they will appear to have dry rot will not kill them but is advisable to try to keep water away in hotter months