In article , echinosum.d0916b7
@gardenbanter.co.uk says...

I think based on what you say I'll chop the tree off about 6 ft above
ground level, and see if it rights itself. If not, I'll cut it lower.

I read somewhere that in their native areas, if damaged by fire they
can sprout again from ground level. I might be tempted to cut it right
off.

I've just had the same problem with a 15ft twin trunked pittosporum;
a gale the other day knocked one of the trunks right out. Thinking the
other half would then be more vulnerable to wind and the same fate I
pruned it down to about 6".

Janet