A Watford man died after the "legal high" he had been smoking caused his lungs to bleed, starving his brain of oxygen.

Jeremy Glasspool was discovered dead by his father on September 16, in Sheraton Mews, Gade Avenue.

In his flat were seven packets of synthetic cannabis, known as a "legal high", and evidence he had been smoking it.

The substance is made in a laboratory and mimics the effects of smoking cannabis, but is undetectable by normal blood tests and is freely, and legally, available to buy on the internet.

At an inquest into Mr Glasspool’s death yesterday, coroner Edward Thomas said the 35-year-old kept himself to himself, but that his neighbours had noticed he had not been his usual self for the past couple of months.

He added: "The housing estate manager saw him and said he seemed confused, and he had telephoned the police saying he was concerned someone was after him."

Mathilda Ralph, consultant pathologist suggested Mr Glasspool was suffering from paranoia as a result of the drug.

She said a post-mortem into his death revealed he had been dead for some time when he was discovered, and had not been looking after himself.

Ms Ralph said: "He looked a lot older than 35 and was very thin. He had an enlarged heart, flabby and dilated, like that of an older person.

"There was blood in both thoracic cavities and into the lungs themselves. There was hemorrhaging all the way up the respiratory tract.

"The initial screening of his blood was clear but I requested a further test, due to what was found in the house, otherwise I wouldn’t have known to do it."

A "mass spectrometry test", a more detailed blood test, was carried out and picked up two compounds of synthetic cannabinoid - a copy of the active ingredient in cannabis.

Ms Ralph said: "The side effects of this drug are still becoming clear, there is not a huge amount known.

"The most documented side effects are convulsions or heart attacks, and I have found two references to pulmonary hemorrhages.

"These are not apparent after just one use; they are more likely to come about after repeated and prolonged use."

In Mr Glasspool’s case the drug damaged his lungs’ ability to work properly, leading to his brain being starved of oxygen.

Edward Thomas recorded death by misadventure, caused by acute pulmonary hemorrhages following inhalation of synthetic cannabinoid.

He added: "Whether legal or illegal, you don’t know the effects of this. It’s very, very dangerous and can have fatal consequences."

James Glasspool, Jeremy’s father, said: "I don’t understand why this is still here when it’s banned in 16 other countries.

"Letters have been sent to Alan Johnson when he was home secretary in 2009, and Jackie Smith, after him asking for these legal highs to be banned.

"This year a letter was sent to Theresa May asking for them to be banned generically so they cannot simply be reinvented.

"I am disappointed that after three months no-one has looked on Jeremy’s computer to find the website he bought it from."