Bruce wrote:

snip

Telegraph poles, for instance, are supposed to last at least 20 years
- quite a few have lasted much longer than this. Although numerous
treatment processes have been tried over the decades, the best (and
probably the cheapest) has always been proper creosote, not just
brushed on to the poles, but pressure/vacuum 'applied', hot, so that
it gets right into the cellular core of the pole.

Telegraph poles also have multiple longitudinal saw cuts around their
perimeter to enable the preservative to penetrate further.

Didn't notice that when I cut up a discarded telegraph pole last year.
What I did notice however was that the visible discolouration got got
nowhere near the the centre of the pole.

I need another section so I will take a closer look when I return to the
remains.