Archaeologists armed with hi-tech gear may have uncovered remains from a legendary English Civil War encampment.
Experts say it could be the first hard evidence of the Fairfax Entrenchment, a military base high above Bingley headed by a top-ranking Roundhead general.
Using technology seen by millions on television's Time Team programme, geophysicists led by Dr John Gater turned up a tantalising subterranean view of a field at the St Ives estate near Harden which may have held part of the encampment Dr Gater, a regular on the Channel 4 show, carried out the painstaking electronic survey on behalf of a group which is aiming to plant a new wood on the site.
The Friends of St Ives want to create a woodland containing British native trees, but they were keen to find out if there was anything of archaeological important around the site before setting out.
Dr Gater said the survey had revealed a mysterious curved ditch which he said could be evidence of the encampment.
"It looks like a large ditch that's got interruptions and it's just possible that's the Fairfax Entrenchment," he said.
"It's known to exist at this point then its course is lost, so it looks as though we may have found it.
"I must be honest, when we came here I wasn't expecting to get anything.
"It really does suggest we need to do a much bigger survey and they will have to be careful just where they plant the trees."
Dr Angela Edmond, of the University of Bradford's archaeology department, has been working with the Friends on the site.
"It's local legend, hearsay, that there was a camp of soldiers on Harden Moor and we know during the Civil War there were an awful lot of skirmishes that took place that weren't actually recorded," she said.
"Legend has it there was a camp on Harden Moor and General Fairfax stayed in Harden village.
"We also understand, again through hearsay, that there were a number of burials near the camp."
Pam Laking, chairman of the Friends of St Ives, said the plan to invite public donations for each new tree would still go ahead, but would be restructured in light of the find.
"This area of land has been set aside for a Friends Wood," she said.
"We cannot plant on top of this trench until we know what it is.
"We'll have to go back to the drawing board.
"We're waiting for the full results from John Gater, then we'll get together with the Council and decide what we're going to do. It's quite exciting."