Illegal metal detecting at historic sites is on the rise, according to a report from English Heritage.

The conservation charity said that December 2019 had seen the largest number of incidents of the practice, also known as “nighthawking”, for any month in four years. It added that there were more than double the number of incidents in 2019 compared to 2017.

Kate Mavor, English Heritage’s chief executive, stressed the impact of the crime. “Illegal metal detecting robs us of our past.” she said. “Once items are spirited away they can never be replaced, and the evidence of those who went before us is lost forever.”

Among the sites targeted by criminals were the Battle of Hastings battlefield in Sussex, Hadrian’s Wall in Northumberland and Old Sarum in Wiltshire, the site of Salisbury’s original cathedral.

Many of the 400 places in the care of English Heritage are unstaffed and free to enter and the organisation is now both reviewing its security arrangements and calling on members of the public to stay vigilant and report any suspicious activity to police.

Illegal metal detecting is undertaken without the permission of the landowner and without adhering to any of the laws that safeguard the preservation of Scheduled Monuments and other protected sites.

Mark Harrison, head of crime strategy at Historic England, added: “Illegal metal detecting is not a victimless crime. We may never see or fully understand the objects taken or damaged because they have been removed from their original sites with no care or record as to their history or context.

“Historic England will continue to work with the Police, English Heritage and the metal detecting community to identify the small criminal minority who are intent on causing loss and damage to our shared cultural heritage and to bring them to justice.”