Triangulation pillars (colloquially “trig points”) were built by the Ordnance Survey to help with the process of re-doing maps of the whole of Great Britain, starting from 1935 onwards. They are normally at the top of hills, though not always. The intention when they were built was that from any one trig point, two others would be visible. Thus if you knew the height and position of an initial trig point, you could use these trig points (and highly-accurate theodolites) to map the positions of trig points across the UK very accurately.

These days, of course, satellite navigation systems are much faster and more accurate. Sadly many trig points are being removed, but there is a certain satisfaction in getting to the top of a hill and touching the trig point there, to convince yourself that you have indeed reached the summit!

There is, of course, a “trig point bagging” community, which seems to be represented by the website https://trigpointing.uk I hope I don’t come across as rude if I say that perhaps the site could do with a little maintenance; I found it hard to navigate my way around it. But once I did get my head around it, I was able to work out that this one, at Wallacestone Park, is TP6707, at a height of 154.966m.

No matter how much I might claim I’m resisting, I just know that I’m going to sign up to the web site…