The Six Trigs challenge walk

In the days when map-making required long hard days in the field and skilled surveyors experienced in the science of triangulation, the Ordnance Survey needed its network of familiar four-foot-high concrete white pillars located on Britain's mountains and hills. Staff would struggle up the hills, erect their theodolites on the pillars and use them to calculate the exact angles to the places they were surveying.

Map-making has moved on, and now satellite technology greatly improved the speed and accuracy with which maps can be compiled and updated. But the network of trig points, some now losing their white paint, remains.

Concrete pillars on hilltops might originally have seemed ugly. Long familiarity, however, has turned trig points into old friends for most walkers, and they provide convenient objectives for walks. Link several trig points together, and they also create challenging day-long walks, worthy of the fittest outdoor enthusiast.

And so it is with the Six Trigs walk, provided here as a final offering for anyone who has undertaken all twelve of the walks in my South Pennines and the Bronte Moors book, or is ready for something (even) more demanding.

Look closely at the OS South Pennines map, and it becomes apparent that a horseshoe of high ground, most of it about 400-500m above sea level, stretches round in an arc north of Hebden Bridge . Inside this arc are enclosed all the tributaries and streams which together make up the waters of the Hebden Water and Colden rivers and which empty eventually into the river Calder. Beyond are other river systems, some ending up in the river Ribble, some in the river Aire.

Ranged along this arc are six of the Ordnance Survey's trig points: at Bride Stones (GR 932268), Hoof Stones Height (GR 913291), Boulsworth Hill (GR 930357), Stanbury Moor (GR 978357), High Brown Knoll (GR 009303) and Sheepstones (GR 014278). The task, therefore, is simply to put them together – to start at Hebden Bridge, visit all six trigs (either clockwise or anti-clockwise), and return to Hebden Bridge several hours later, tired but satisfied.

The idea for the ‘Six Trigs' was first floated late in 1999 in an article by the current author in the outdoor magazine TGO. At the time, the point had to be made that the Six Trigs route crossed private land and would have to wait – at least for anyone not wanting to have to trespass – until the access legislation was in place. TGO kindly described the route as a ‘soon-to-be classic'.

That time has now come, and the Six Trigs is available to all. The route is about the same length as a marathon (26 miles/ 42 kms), and although there is little climbing after the first pull-up from the Calder valley, the ground is in places hard going. Anyone attempting it walking will probably take about ten hours to complete (runners will be able to knock some hours off that time). The route includes the high moorland of Black Hameldon, the Boulsworth Hill plateau, Crow Hill and the Alcomden Stones, Top Withens and Oxenhope Stoop, and High Brown Knoll.

There are no badges or certificates for completing the Six Trigs, and there is no organisation to congratulate you on your achievement. What you will gain on the other hand is the pleasure of a hard day's walking, and the understanding that comes from a comprehensive introduction to some of the finest of the south Pennine moors.

The book South Pennines and the Bronte Moors by Andrew Bibby is one of the guides in the Freedom to Roam series published by Frances Lincoln and the Ramblers' Association.

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