A proposed wind farm would have “minor adverse significance” on the setting of nearby listed buildings, an inquiry was told.

Andrew Brown, for wind turbines company EnergieKontor UK, claimed the impact on grade two star listed Gledstone Hall and Ingthorpe Grange would be minor – although he said it would be up to the inspector to decide what constituted “setting”.

He did, however, say that the impact on Steeling Hill Enclosure – a defensive Iron Age enclosure 1.5 kilometres away from the turbines site – would be substantial.

Earlier in the inquiry, Craven District Council’s heritage expert said the impact of the turbines on the Iron Age enclosure would be such that the significance of its location – with uninterrupted views – would be lost.

Speaking on the fourth day of the inquiry into the building of five 100- metre-high turbines at Brightenber Hill, near Gargrave, Mr Brown said he was not seeking to downgrade the importance of Steeling Hill – classed as a scheduled monument – but pointed out it had no public access.

“The monument has very limited aesthetic value as it now consists of poorly defined earthworks. Also as there is no public access, I consider that it has limited communal value,” he said.

But he conceded: “It is my opinion that the proposed wind turbines will seriously damage the overall value and appreciation of the Steeling Hill enclosure and the magnitude of effect will therefore be substantially adverse. Given the national sensitivity of the scheduled monument, this equates to an impact of major adverse significance.”

Mr Brown, of Leeds-based Woodhall Planning and Conservation, also accepted that views of the turbines from footpaths close to the monument would be clearly visible and would be “major features”.

Views from Gledstone Hall – designed by celebrated architect Sir Edwin Lutyens in the early 20th century – would not be greatly affected because major rooms looked to the south and not to the north where the turbines would be.

He added that views from 17th century Ingthorpe Grange – originally a working farm for Bolton Abbey – would be very limited.

He accepted that the turbines would “change the overall value of the listed building” but that they would not “sever it from its immediate setting or result in any loss of integrity”.

His views contrasted sharply with Craven District Council’s David Hodgkinson, who spoke earlier in the inquiry about the impact of the turbines on the area’s heritage. Mr Hodgkinson, technical director responsible for heritage projects with Staffordshire-based environmental consultants Wardell Armstrong, said the council had been right in refusing planning permission for the turbines on the grounds of their unacceptable impacts on the area’s heritage assets.

Mr Hodgkinson said that the mitigation measures proposed by EnergieKontor would not have any noticeable reduction to the impact.

And he said the impact on the settings of Steeling Hill, Ingthorpe Grange and Gledstone Hall would all be of “high significance”.

Steeling Hill, scheduled in 1964, enjoyed “unrivalled expansive views in all directions” – a “key feature” of why the site was chosen, he said.

If the turbines were built, there would no longer be uninterrupted views to the south and “the appreciation as to why the enclosure was sited in that specific location would be diminished and would remain diminished throughout the life of the scheme.”

In his evidence to the inquiry, Mr Hodgkinson said uninterrupted views to the north and distant hills had been instrumental in the selection of the site for Gledstone Hall.

On Tuesday, the inquiry heard that the views, particularly to the north, were almost the same as they had been when the house was built.

The inquiry, being held at the council offices in Granville Street, started on Tuesday last week.

Planning inspector John Braithwaite spent Monday viewing the proposed site from private property, but will return to view it from public footpaths – as there was poor visibility on the day.

Craven District Council went against the advice of its outside planning consultants and refused planning permission for the wind farm in December 2008.