Walking groups fear a historic ruin in the Washburn Valley has now become ‘out of bounds’.

John of Gaunt’s – or John O’Gaunt’s – Castle, the remains of a royal hunting lodge that dates back to at least the 14th Century, has been used for decades by walkers as an interesting rest place.

But recent visitors have been shocked to see a “No Admittance, Under Private Ownership” sign appear by the site at Haverah Park, near Beaver Dyke reservoirs.

One walker, who was out with an Otley group when he came across the warning, has now raised the issue with Washburn Parish Council.

The man, who did not want to be named, said: “I don’t know what has happened to John of Gaunt’s Castle or who owns it now, but I was shocked to see this sign up, as walkers have been stopping there for years.

“The councillors – at the annual parish meeting – said they were unaware of any restrictions to public access but are going to enquire about them.

“One lady at the meeting did say her friend had been walking her dog there the other day and had been confronted by the builder who told her to keep out of the now ‘private’ castle area.”

Harrogate Borough Council, in November 2012, approved a plan to convert barns at the site into a single building along with the “installation of a package treatment plant”.

English Heritage did not raise any objections, concluding that the development area was “immediately adjacent to, but outwith the boundary of, the Scheduled Monument of John of Gaunt's Castle.”

In its comments to the planners, the organisation added: “The proposed development will not constitute a negative impact on the significance of the Scheduled Monument or its setting.”

The local Ramblers group, though, did object, highlighting its main concern as being what would happen to the footpath that runs east-west along the south side of the site.

Keyland Developments, one of Yorkshire Water’s sister companies, was the landowner at the time but the plot was sold on last year.

An English Heritage spokeswoman said: “John O’Gaunt’s Castle is a protected as a Scheduled Monument.

“About ten years ago under previous ownership the site was in a vulnerable condition and on our 'At Risk’ register.

“We provided a grant to consolidate the site and it was taken off the register.

“Like many Scheduled Monuments and Listed buildings, the site lies on private land and is not subject to conditions guaranteeing public access.

“We help celebrate and care for the best of England’s heritage - which in many cases involves working with private individuals and companies who own and look after historic sites. In this case the owner is within his rights to restrict access to the monument.”

The report commissioned by English Heritage in 2004 records that the spot is named after John of Gaunt, Duke of Lancaster, who acquired the lodge from the Crown in 1372. It goes on to state that the building may have been originally established as early as the 12th century, though “the first known reference occurs in 1333 when substantial repairs – ordered by Edward III – were undertaken to an existing building.”

The lodge once had a moat, a curtain wall and a central tower and included chambers, a chapel and a gatehouse.