Nestling in the shadow of a white horse and a Neolithic long barrow, in a renowned crop circle hotspot, Alton Priors, in Wiltshire, feels like the perfect venue for a spot of water witchery. Prompted by the news that Thames Water and Severn Trent Water use dowsing rods to detect water leaks, I’ve arranged to meet my mum – a geologist and amateur dowser – to investigate the phenomenon for myself.

There are other reasons for picking this particular location. Geologically speaking, Alton Priors lies on the boundary between a chalk escarpment and sandstone, the latter underlain by clay, which means there are numerous springs gushing out of the ground. The local churchyard is also where an acquaintance of my mum once suggested she try dowsing, because “he just had a sense it would work there”. Sure enough, her rods crossed.

My mum isn’t generally prone to magical thinking. An expert on the geology of Wiltshire, and a trained Blue Badge tourist guide, she was first given a pair of dowsing rods when she started taking tour groups around Stonehenge. To her surprise, the rods crossed, piquing her curiosity. Since then, she’s discovered they reliably cross for her over water, trees, ancient henges and barrows, as well as the long axis of churches.

To sceptics, this may sound like a classic case of confirmation bias: the tendency to interpret information in a way that confirms or supports our prior beliefs. If you are expecting a pair of dowsing rods to cross in particular locations, and they do, that’s evidence that dowsing works.

Not so fast, says my mum. There are other locations where she fully expected them to work, and they didn’t, such as iron age hill forts. She doesn’t know why they cross over certain features and not others, but they do – and she strongly suspects water is involved.