The first problem with ley lines is defining what points shall be considered significant on a ley. Alfred Watkins had a points system which graded the markers. Paul Screeton's Ley Hunter definition is probably as good as any here.. This is always going to be subjective, but they fall into two classes - direct markers and indirect markers.

Direct markers are therefore sites of obvious prehistoric provenance. Indeed, one variant of the ley theory, John G Williams' SCEMB lines, limits itself to just those elements. Ley researchers also accepted indirect markers, such as some churches and crossroads, on the ground that these were often sited on previous prehistoric sites.

The essential thesis of leys is that prehistoric man sited many of his markers along straight lines on the ground.

Straight lines would ideally imply a great-circle route, though over the 10-mile stretch of significance for leys a straight line on the OS map projection would be acceptable.

Accepting these, the factual questions boil down to

1. Are the described sites on a straight line as stated, within an acceptable accuracy?
2. Is a straight line in the field the same as a straight line on the map?
3. How does the number of ley lines in an area compare to the number of alignments you would get from the same number of significant points as the original map had, but scattered at random.

Softer questions are

• Would Neolithic Man be able to align his monuments with such accuracy?
• and perhaps the killer question - why go to all this trouble?

Most of these are contentious, though it was the first and last factual points that Williamson & Bellamy showed devastatingly to be the key weakness of the ley theory.

The "acceptable accuracy" of point 1 is a practical issue, since the symbol for many types of site varies. A church symbol occupies 50 yards by 45 yards on the ground on a 1:50,000 scale map, and even the finest pencil dot is 17.6 yards in diameter on that scale The only sites that approximate a dot are standing stones, wells and churches without towers. Obviously a real church is often even larger than the symbol, but its extent means that there is more chance of such an object intersecting a ley than the width of the pencil line would seem to indicate.

This looks trivial, but shows how one's intuitive grasp of the uniqueness of a ley is at fault. Williamson & Bellamy showed how for example increasing the size of two out of 11 point elements changed the number of leys in their example from four to nine.

The coup the grace came when Williamson & Bellamy took OS sheet 173 (Swindon, Devizes in Wiltshire) which includes Avebury. They looked for leys, coming up with the following.

which is a pretty convincing confirmation of the ley system. Until you take into account the number of leys they discovered when they randomised the positions of these points within their grid squares (or four squares in the case of larger area sites)

That's it. 'nuff said. End of story. Leys are toast - at least as far as searching for them as straight line alignments using maps! Of course, I would have liked to have seen the exact leys Williamson & Bellamy found, the positions of their mark points in Grid refs and the positions of their randomised mark points to reproduce their results and confirm no undue fiddling went on. Yet is is the problem of the area points, and the subtle and counterintuitive way they make leys so much more common than one would expect, which is where I found their case strongest. I have not heard of a ley comprising more than five megalithic point marks.

Their work doesn't fundamentally disprove that some prehistoric stones were aligned intentionally, but what it does do is state you simply can't tell if they were from the fact that alignments do exist. You can't eliminate Type 1 errors, so you can't tell intention from finding straight line alignments, because straight line alignments can be found in a randomised plot which has no intentional alignments by definition. It wouldn't be so bad if the alignments tended towards one direction, like recumbent stone circles tend to have the recumbent stone aligned to the south-west, so the arc of the southernmost moon grazes the recumbent stone. But no such anisotropy is found with leys.

The end of the dream

Leys didn't die - they faded away and became distorted into nothingness. The conversion from Watkins' impossibly straight pathways through forests, across hills and rivers and through bogs to the energy lines of the 1970s coincided with a change in editorship of "The Ley Hunter" to Paul Devereux. Disturbed by the subjectivity of the dowsing approach, and yearning for academic recognition, Devereux launched the "Dragon Project" which was an attempt to measure these subtle forces via a range of effects - magnetic fields, electric fields, nuclear radiation detectors, ultrasound and others physical means.

The results of the physical monitoring part of the Dragon project were inconclusive, though once again the difference between amateur research and professional research shows in the total absence of published documentation, other than Paul Devereux's book Places of Power which is a summary of the work aimed at non-technical readers.

Don Robins, one of the initial researchers, also wrote an earlier book before the project was finished titled Circles of Silence which indicated a more positive result. Nowhere are details of the equipment used, the methodology detailed or field notes described in sufficient detail to attempt to replicate any of the work. This is a shame, particularly as the book gives the impression that there were observations worth following up. Danny Sullivan summed it up that "The conclusion was that apart from variable and rare anomalous features in the earth's geomagnetic field, natural background radioactivity and ultrasound there was no evidence at all for an unknown 'earth force'".

The 1983 Williamson & Bellamy book seems to have finished off the subject in terms of ancient energy networks, though you still read widely on the web and in books words to the effect of "Leys are lines of mysterious ancient power, along which prehistoric man aligned his monuments". The ley hunters up to mid-1980s went on an intuitively very reasonable premise - that the alignments were significant and unlikely to occur by chance. A premise which turned out to be incorrect. After this, evidence was mustered from disparate and unconnected ancient societies across the whole world, to draw a tenuous conclusion.

Ley lines revisited: The death roads thesis