One of the “unashamedly modern” homes set to be built on the site of Bath’s historic Waterworks Cottage when it is demolished can now be even bigger than previously planned after an “ultimatum” from the applicants promoted a council U-turn.

In November, councillors on Bath and North East Somerset Council’s planning committee had turned down the application to increase the size of one of the two modern homes planned for the site to fit an extra bedroom. But councillors have now overturned that decision after a “gentleman’s agreement” was offered that the owners would give up their rights to extend the house any more.

The planning battle between the council and cottage owners Jeremy and Sarah Flavell over demolishing the cottage and building modern homes on the site has now gone on for more than three years and tied up more of the council’s time than many decisions over considerably larger developments.

It has already been ruled that the cottage can be demolished. The whole matter appeared to have been settled in the summer, when the council finally granted approval for two “unashamedly modern” houses to be built on the site — only for the Flavells to come back with their application for one of the new houses to be allowed to be even bigger.

After councillors refused this, their agent Tom Rocke emailed the council to threaten an appeal which he said could also seek to recoup legal costs from the council. But he added that if the council changed their decision and accepted the extension, the Flavells would be prepared to give up their “permitted development” rights to the house they hope to expand.

Permitted development allows some buildings to be extended by up to 30% of their size without the need for planning permission. Mr Rocke told the planning committee at their meeting on November 13: “More than two and a half times the volume could be added under permitted development rights than my clients are seeking permission for through this application.”

Waterworks Cottage’s next-door neighbour Chris Parkin warned that the permitted development rights could allow “unfettered expansion.” He said: “I therefore encourage the committee, despite the applicant’s ultimatum, to uphold the decision to refuse the proposed variations — and to request the removal of permitted development rights.”

Westfield councillor Eleanor Jackson said that she had voted against the extension of the new house at the November meeting, but told councillors: “I think we have to face reality.”

Ian Halsall, councillor for Oldfield Park, added: “Given the gentleman’s agreement from the applicant and they have said in public that they are happy to have their [permitted development] rights removed if they are allowed to have this modest increase, then I think we have a compromise there.”

But Midsomer Norton North councillor Shaun Hughes said: “I have been involved in every revision of this site application under various guises it’s been presented in and my conclusion at every stage has been that this is an overdevelopment .”

He added: “I find some of the design aspects overbearing and, for me, any additions to this are not acceptable. I think it has already exceeded what I would have considered to be acceptable.”

Councillors on the planning committee voted to accept the offer as set out by Mr Rocke, permitting the proposed enlargement of the house but removing its permitted development rights to be extended any more without planning permission.

But the Flavells will retain the permitted development rights to extend the other home if they wish to, as Mr Halsall noted: “We have missed the boat on that one.”

Waterworks Cottage overlooks Chalcombe Valley and dates back to the 1850s, when it was probably built as accommodation for the workers at the nearby waterworks. Although it is not listed, it has been a non-designated heritage asset locally since 2017.

The demolition of the cottage has been a major point of controversy. The Bath and Counties Archaeological Society called it “a significant and irreplaceable loss to the local heritage.”

LDRS, John Wimperis