The controversial Hampstead Heath dams project is not “absurd or irrational” and is backed by a weight of expert opinion, the High Court heard today.

Opponents of the £15million scheme have presented a “weak case” which disappears “into the distance” when you consider engineers’ views, David Elvin QC said.

“It can’t be in the interests of users of the Heath to have a system of dams which places people and ponds at risk,” he added.

Mr Elvin appeared for the City of London Corporation to defend against a judicial review challenge brought by the Heath and Hampstead Society, which is leading the campaign against the project.

The hearing came to a close this afternoon and the judge, Mrs Justice Lang, could be set to give her verdict as soon as next week.

The legal battle is the culmination of years of wrangling over the future of the Heath’s ponds.

The society and its thousands of supporters fear the project will lead to the “permanent disfigurement” of the landscape.

Yesterday, the society’s barrister Stephen Tromans QC argued that the Heath is an “exceptional case” and its ponds should not be treated like any other reservoir.

He claimed it was irrational and legally flawed to redesign the ponds to “virtually eliminate” any risk of collapse even in a worst case scenario storm.

But Mr Elvin today countered that the Heath’s ponds are not at all exceptional.

He said there are many dams across the country in sensitive or picturesque areas with special protection – and they must all conform to the same standards.

Three of the Heath’s ponds have been deemed Category A dams by an expert engineer – the highest risk category – meaning safety overrides all other considerations, he argued.

Statutory protection of the green space’s “natural aspect” under the Hampstead Heath Act does not restrict what must be done to protect the public, the court heard.

He said there is “nothing unsurprising” about the Heath’s dams and the fact the work must be carried out is “just one of those things”.

He added: “This is the result of a lengthy exercise over six or seven years by expert engineers to reach this solution.

“The fact is, this is a case where we have absolutely no contrary expert evidence from the claimant.

“We have entirely one-sided expert evidence, when being urged to find things absurd or irrational.

“What we don’t have is any engineer suggesting the City’s approach is absurd or irrational in any way, or that it offers a solution that is not to be expected.”

Much of the case hinges on the weight afforded to guidance issued by the Institution of Civil Engineers (ICE), which is where the pressure to “virtually eliminate” all risk derives from.

The society argues this is not a legal requirement and the guidance should not be “elevated” into being an inflexible standard of safety.

But Mr Elvin said: “Parliament has left the guidance here to engineering experts…

“The ICE guidance is guidance which is supported by Defra.

“It’s not statutory guidance – but it’s the next best thing.”

He said it is “unacceptable on anyone’s view” that the fatality rate could be more than 1,000 in the worst case scenario storm, if nothing is done.

He also criticised the society’s emphasis on early flood warning systems to mitigate risk, saying it is the established practice not to take these into account when assessing dam safety.

He continued: “The attempt of the society to downplay the risk lacks evidential support.

“The idea you can wait for an early warning system or expect people to get out of their flats as soon as the rain starts is not realistic.

“Evacuations are tricky things to manage, and we do not rely upon early warning as a means of dealing with dam collapse.

“The way to do it is by making sure a dam is built to sufficiently high standards.

“The approach of the society is simply incorrect and the approach taken by the City is entirely rational, following ICE guidance and methods applied by engineers across the UK.”

See next week’s Ham&High for more coverage.