A man was killed trying to steal a copper cable which was carrying 11,000 volts, an inquest heard today.

Kirk John Thompson was electrocuted at the derelict Panteg steelworks, in Pontypool, South Wales, when his bolt croppers pierced the plastic coating of a cable still connected to the National Grid.

Britain has been hit by a plague of of metal thefts in recent years as the Asian construction and manufacturing boom has pushed up the prices of raw materials.

Thieves routinely rip long sections of copper cable from the side of railway lines or steal lead flashing from church roofs - ignoring health and safety warnings from the police and quickly melting down their loot.

In 2005, a two-tonne bronze statue by the sculptor Henry Moore, valued at £3 million, was stolen in Hertfordshire. Police believe that it was taken for its scrap metal value.

The inquest in Newport heard that the body of Thompson, 43, was discovered outside the perimeter fence of the steelworks on the morning of April 10 this year.

Two men, who were later arrested, told police they went to the site in the early hours of the morning with Mr Thompson to steal copper. They said they carried him from the scene of his death and abandoned him when they thought someone had seen them.

Mr Thompson’s sister, Samantha Hopkins, told the inquest in Newport that her brother was unemployed and had been a heroin addict, although he had been "totally clean" for the past eight months.

Detective Constable Gordon Poole of Gwent Police said Mr Thompson had been at the steelworks a few days before his death to steal some copper. He added that electricity to much of the site had been shut down when an attempt to cut copper wire with an axe had pierced a live cable carrying less than 500 volts.

Despite this, the detective said there were still live cables running to the site’s sub station. "Scenes of crime subsequently found out one of these cables had a direct connection to the National Grid and was carrying 11,000 volts," said DC Poole.

A post-mortem showed that he had died of electrocution.

The deputy coroner for Gwent, Wendy James, said toxicology tests found amphetamines in Mr Thompson’s bloodstream consistent with "recent abuse" which she believes would have increased his risk-taking.

"Mr Thompson had no right to be at the site," said Miss James. "It is perfectly clear he ignored all the warnings over the dangers of electricity.

She added: "Never has the old saying ’crime never pays’ been so graphically illustrated as in this case. These type of thefts are on the increase and people should heed the warnings of the dangers of electricity. If they choose to ignore the warnings they will pay the highest price possible."

She recorded a verdict of accidental death.

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