The possible archaeological significance of a Harpenden Green Belt site should be “thoroughly investigated” before a proposal to transform it into a new secondary school becomes a reality, a PhD student has urged.

Alexander Thomas is “extremely concerned” that no allowance is being made for the heritage value of land on the corner of Lower Luton Road and Common Lane, currently the base of a long-running cattle-raising farm.

The Batford farmland has been earmarked by Herts county council for a new six form of entry school, as proposed by local consortium the Harpenden Secondary Education Trust and backed by school campaigners.

But Alexander said: “The school needs to be positioned in the right place, but for heritage reasons, this isn’t the right place.”

He warned that fields at the site “contain interesting earthwork features including demolished buildings in the south-west corner which seem to be associated with Batford Mill.

“Old maps show this relationship and also indicate these are possibly medieval or post-medieval in date - AD1200 to 1800.”

The 25-year-old is studying his first year of a doctorate in archaeology and anthropology at the University of Bristol and his research concerns the archaeological ‘visibility’ - or remains - of the Danelaw boundary, a region where Danish law was once recognised during the late 9th-11th centuries.

He said: “One of my areas of research is Harpenden around the River Lea, an area in which I have a personal interest as I grew up in Harpenden and my family lives there.”

Alexander said the Batford farm contained traces of an ancient field boundary and was, “very close to the ancient ford and River Lea, which was the Danelaw boundary in the Anglo-Saxon period and Viking age, where the original settlement of Harpenden appears to be centred.

“The position of the field is also significant as it forms part of the link between the ford, Mackerye End and the Roman villa at [Grade II listed] Turners Hall Farm.”

Alexander said: “If you look at historic maps of the area you see what are possibly post-medieval buildings that seem to be associated with Batford Mill, which seems to be recorded in the Domesday Book.”

A spokesman for the county council said the archaeological significance of any site earmarked for development “must always be considered.

“This was the case during the process of identifying secondary school sites at Harpenden, when a consultant was commissioned to review each of the [nine potential] sites.”

A consultant’s report to the council said the likelihood of prehistoric and medieval archaeological assets was “very low”.