Dyfed-Powys Police has stepped up patrols in Carno, near Newtown, to warn off criminals attempting to unearth a stash of the drug, which former detective Stephen Bentley believes is hidden nearby.

In 1977 a large police operation, involved 11 forces over two years and ended with officers raiding an old mansion and pulling down a multi million drugs empire.

More than a million tablets were seized, and the operation said to have been responsible for supplying 90 per cent of the LSD in the UK.

In a new edition of his book on the story, Undercover: Operation Julie – The Inside Story, Mr Bentley revealed he believes a second stash of LSD was never found.

This has prompted Dyfed-Powys Police to increase patrols in the area to stop people from travelling to dig up the Class A drugs.

Alana Perrin, a Dyfed-Powys Police spokeswoman, said: "Dyfed-Powys Police are aware of the issue and are assessing the content of the disclosure.

"We will be checking the records we hold to establish whether or not matters raised warrant further investigation.

“In the meantime we will be making the current owners of Plas Llysyn aware of the disclosure and the potential for persons to visit the area in an attempt to locate the drugs. We will be providing them with reassurance through increased patrols.

Advertising

“We would also like to make it clear Dyfed-Powys Police take a robust approach to drug trafficking and that appropriate action will be taken in respect of anyone suspected of using the information disclosed to assist them in obtaining and supplying controlled drugs.”

Mr Bentley was one of 800 officers who worked on the case in the 70's.

The operation first began in 1975 when chemist and ringleader in the operation Richard Kemp was involved in a fatal car crash in Machynlleth.

Police pieced a torn up note together is mentioned a key LSD ingredient.

Advertising

It gave them their first clue, and a two and a half year operation began with officers dressing as hippies to get in with the drugs gangs.

At times they had to fight police officers to maintain cover, and when suspected of being a gay cult, female officers were introduced.

After months of investigations, police swooped in 1977 to find one million tablets, and raw materials to make a further 6.5 million.

120 arrests were made across the UK, with 15 convictions resulting in prisons sentences of 120 years, and overnight the price of LSD in the UK was rumoured to have risen from £1 a tab to £5.

A stash was found in Tregaron, West Wales, but a second stash was never found and after seeing a statement, Mr Bentley says it is still undiscovered.

Mr Bentley said: "Kemp was furious when he found out that the police had discovered this major hoard of acid and made a voluntary statement to police on December 30, 1977.

“He revealed what I believe to be the whereabouts of a further stash of acid.

“At no point is there any mention of police digging up and retrieving this stash."

Mr Bentley said no search was made for the drugs by police, and hopes they don't fall into the wrong hands.

He said: "Hopefully, if it is still out there, the proper authorities get hold of it and dispose of it rather than it ending up in the wrong hands.”