Cavities in trees
We were asked to climb and inspect a very large horse chestnut tree in Lichfield. The tree had been subject to very heavy reductions in the past, where limbs had been shortened back to points where the wood was up to 450mm across.
Almost every single limb reduced, 30+ in this case, had become heavily rotten on the inside.
This tree had also been struck by lightning in the past. This can be seen by the strip of lost bark running down the stem, decayed in some places, but we'll occluded in others.
Even though the works adhered to BS3998, this does not mean that it is always the best thing to do.
Be careful what you do to your trees, seek a professional, trained and educated arboriculturalist.