This 18th century fireplace is testing the Irish heritage laws. It was bid to €110,000 (£77,500) but the local council announced that – although not fitted in the property until the early 1970s – it is now an essential feature of the house.

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The chimneypiece - an exceptional two-colour marble neoclassical mantel with period engraved brass Dublin register grate - was included in the October 17 house contents sale conducted by Sara Kenny Fine Art at Lios an Uisce, a substantial Georgian house in the Dublin suburb of Blackrock. Some lively bidding pushed its final price to €110,000 (£77,500), more than five times the estimate.

However, Dun Laoghaire-Rathdown County Council immediately let it be known the mantelpiece could not be removed by its new owner.

"We are not happy about the sale," said a spokesman. "As far as we are concerned, the mantelpiece is an essential feature of the house, which is a protected structure." The council, he added, had served the owners with an enforcement order under guidelines laid out by the Department of the Environment in 2001, warning that the mantelpiece "should be left intact in the house".

The auctioneer, Sara Kenny, said it had been made clear to the vendor and prospective buyers prior to the sale that the piece was being sold subject to the approval of the local authority. However she added that the chimneypiece, while complementing the interior, was not an original feature of the house. "It was a wedding present to the owners in 1972, as I understand it," she said.

She declined to identify the new owner of the mantelpiece but said he was Irish "and lives not too far from Dublin". There had been a lot of interest in the piece, with four or five bidders on the floor and a similar number on the phones. "The price stalled at €65,000, then took off again. It was very competitive."

The current difficulty, she believes, will be resolved in talks between the purchaser, the house owners and council officials - a decision-making process that is allowed up to 12 weeks. She did, however, agree that there would be wider repercussions if the sale was not allowed to go through.

Asked about the next move, the council spokesman said it was for the house owners to respond to the enforcement notice. "People are entitled to make their case and we will assess that. The ball is in the applicant's court."

Christie's and HOK fell foul of the 2001 heritage laws in 2003 when An Taise, the Irish National Trust, attempted to halt the sale of seven ormolu gasoliers from Lissadell House, Co. Sligo on the grounds that - although not part of the original architect's vision - they were of "technical importance" to the property.

A private treaty sale was arranged with the new owners of the building and legal action was dropped.

By Anthony Garvey