"Snowman" wrote in message ...
This morning about 5 am we were awoken by a creaking, splintering sound and
discovered later that a large branch had broken off a large mature ash tree
at the bottom of the garden.

No wisdom to offer, but fascinated to read this thread. I had exactly
the same experience - albeit on a much smaller scale - about 2 weeks
ago with an 8' long branch of lilac tree. It was a baking hot
afternoon with no wind, and I assumed ants might have eaten away at
the wood, but that break too was clean. I was actually quite pleased,
as I'd wanted to prune the tree. Only problem now is, how to get rid
of the wood... where's an axeman when you need one?