One of the country’s richest men sparked an ecological disaster when he tried to turn an overgrown reservoir on a sprawling Scottish estate into his private fishing pond.

The attempt by Paul Thwaites, 55, to create a private fishery on his £5.5 million estate led to one of the worst pollution incidents ever recorded by the Scottish Environment Protection Agency (Sepa).

Property developer Thwaites – whose £180m fortune ranks him 397th richest in the UK – was charged with polluting an important salmon and trout river.

However, the charge was dropped without explanation by the Crown yesterday as his contractor Richard Philp took the blame for the environmental catastrophe.

Philp, 50, of Quiech Court, Milnathort, admitted carrying out a controlled activity

likely to cause pollution to the water environment on March 17 and 18 last year.

Perth Sheriff Court was told that a sub-contractor had simply smashed through the reservoir wall with a digger and caused the water to empty into a tributary and then the River Earn.

As a result, 1000 tonnes of silt poured into the fresh water and destroyed vital spawning grounds for brown trout, sea trout and salmon. A total of 15 kilometres of river was affected.

The court heard that the full-scale of the ecological impact would not be known for several years, but whole generations of fish could be lost as a direct result.

Fiscal depute Janine Bates said: “As a result of the silt entering the water course, substantial damage was caused to recently spawned salmonids and other marine life. The eggs were vulnerable to suspended solids pollution. The smothering of them will have impacted on future numbers. The silt was released into the river at a critical time in the life cycle of the salmonids.

“The reservoir had been drained of water. The ecology had been severely affected. This is one of the worst incidents Sepa officers in Perth have dealt with.”

Miss Bates told the court that Philp had formerly been a fishery manager and had set himself up as a consultant. The disaster at historic Whitehouse of Dunira Estate was his first job in that capacity. The court was told it was also his last, as he was now working as a plumber.

Philp had tried to persuade Mr Thwaites not to start the work in February, but had been persuaded to get on with it as his client wanted to convert the reservoir into a fishing pond.

Miss Bates told the court that, when it was tested, the polluted water had 237 times more silt than a sample from an unaffected part of the river.

“It was entirely foreseeable that works in the reservoir would result in the release of suspended solids unless prior plans were put in place,” she said. “No consideration was given to pollution prevention measures. He [Philp] appears to have been completely ignorant of controlled activities regulations.

Solicitor John Bain, defending, said: “This project was his first and last. Things went pear-shaped. Effectively a breach was made and it just got bigger and bigger.

“He did it once, but will never go near a project of this nature again. He is extremely sorry. He has regretted it ever since. This is attributable to his lack of experience.”

Sheriff Lindsay Foulis described the impact as “disastrous” and said it would be significant along a lengthy stretch of the River Earn. He deferred sentence for social background and community service reports.

The court was told Mr Thwaites, from Barton, Cambridge, no longer owned the Whitehouse of Dunira Estate.