Due to unforeseen circumstances, this event has been rescheduled and is now taking place in July. For those already booked onto this event, please check your email for further updates. Thank you.

April 2026 marks 90 years since trig pillars were first used in the retriangulation of Great Britain. To celebrate, join us for a guided walk to a primary trig point on Tregonning Hill, exploring this hill’s role in early modern mapping and its much older history as a place of settlement and defence. 

Date: Saturday 25th July (rescheduled date)
Time: 3.00pm – 5.30pm 
Location: Tregonning Hill, Balwest, Helston, TR13 9TE – What3Words: ///grain.surpasses.good

Meeting point: Balwest Chapel Car Park, TR13 9TE – What3Words: ///perkily.table.dolls

Price: £10 per person

Trig points were positioned so they could be clearly seen from one another. From Tregonning Hill, there is a direct sight-line to a trig point on Castle an Dinas (West), another important site in Cornwall Heritage Trust’s care. 

If the weather is clear, we should be able to see this concrete pillar. These inter-visible sites would have worked together to help Ordnance Survey surveyors create accurate maps of the surrounding landscape.

Along the walk, we’ll consider how trig pillars were used, why Tregonning was chosen as a survey site, and how the hill has been important for thousands of years, including during prehistory when it was used for its long-distance visibility.

The walk will be led by Cornwall Heritage Trust’s Sites Project Manager, Carolyn Kennett.

Accessibility and terrain

The route is on established paths, however there is rough, uneven ground with steep sections. Sturdy footwear and appropriate clothing are essential.

There is a toilet available near the site.

This event is in aid of Cornwall Heritage Trust – the independent charity protecting Cornwall’s heritage for everyone.