Opponents of the Hampstead Heath dams project insist the fight is not over after losing their High Court challenge – and they are set to lobby the environment secretary and Camden Council.

Mrs Justice Beverly Lang this morning rejected the Heath and Hampstead Society’s judicial review.

She found in favour of the City of London Corporation’s case that the Heath’s dams must be able to withstand the most extreme storm imaginable.

The City manages the Heath and is behind the controversial £15million engineering scheme.

Mrs Justice Lang agreed that the City is right to attempt to “virtually eliminate” the risk of dam failure or collapse even in a catastrophic storm with an astronomical 1-in-400,000 chance of happening each year.

But the society insists it will continue to battle the project, which it fears will cause irreparable harm to the Heath’s landscape and its ponds.

Marc Hutchinson, chairman of the society, said the society was “extremely disappointed”, but made it clear there are no plans to give up the fight.

He said the focus will now turn to the planning application submitted to Camden Council by the City.

He said that during the judicial review hearing, the City’s QC accepted that Camden Council is not bound by the Reservoirs Act – which led to the City’s attempts to virtually eliminate any risk – and has the power to reject the designs.

The society will also lobby Liz Truss, the environment secretary, and ask her to block the project.

Mrs Justice Lang refused an application to appeal when she handed down her verdict this morning, but Mr Hutchinson, a solicitor and pond swimmer who lives in South End Green, said the society can apply directly to the Court of Appeal for the right to appeal.

Mr Hutchinson plans to meet the society’s barristers this week to discuss an appeal.

He said: “The most interesting thing which came of the trial is that the City accepted, as we believed was the case, that Camden Council could require the City to make changes to its designs.

“Camden Council are not bound by the Reservoirs Act and we will be lobbying Camden Council further in connection with the planning application.

“Camden Council have commissioned an expert peer review by [engineering firm] Aecom, who are themselves expert engineers, and it will be very interesting to see if the Aecom report agrees with the recommendations of Dr Andy Hughes [the City’s expert engineer].

“There’s certainly scope for Camden to insist on changes to the designs that are proposed.

“We would ask all those who have not yet written objections to Camden Council to do so, it’s clear the council has a role to play in the final outcome of this project.”

The project will see large new dams built on the Heath and major changes at some areas, including the Catchpit valley and the Model Boating Pond.

The City hopes to win planning permission within the next couple of months and begin the two-year project early next year.

If it goes ahead, heavy duty vehicles including five-tonne tankers, nine-tonne dumpers and a 90-tonne crane will make thousands of trips in and out of four entrances to the Heath.

Twelve ponds across the Heath will undergo works for between four and 33 weeks each, including the three bathing ponds. The ladies’ pond will be shut from mid-February 2016 until mid-May 2016.

The society had argued that the project was legally flawed because there are exceptional cases, including Hampstead Heath, where a reservoir owner does not only have to follow an expert engineer’s opinion on the required standard of safety.

Mrs Justice Lang rejected this argument, deciding it was for the experts alone to make a judgement on the safety standard.

In the Heath’s case, Dr Hughes, a member of a special panel appointed by the secretary of state, decided risk must be virtually eliminated because dam failure would pose a threat to life in downstream communities such as Gospel Oak.

Mr Hutchinson added: “We’re extremely disappointed with the outcome of the case.

“We believed in the merits of our case and the judge agreed that we had an arguable case, which is why she gave us permission to proceed to full judicial review.

“The reason we lost the case is that the judge decided that, under the Reservoirs Act, it is for the expert dam engineer to form an expert opinion on the standard of safety that should be applied to the dams on Hampstead Heath.

“In this case, Dr Andy Hughes applied his expert opinion and decided that the City must virtually eliminate the risk of the dams collapsing.

“Therefore, the project has been designed to ensure the dams will not collapse in the largest imaginable storm, which has been calculated to have a probability of 1-in-400,000.”

Mr Hutchinson said the Reservoirs Act is a unique piece of legislation that requires a higher standard of safety then even the nuclear power industry.

Mrs Justice Lang ruled that the society will have to pay the City’s costs, although this payment was capped at £10,000.