John Roberts, aged 39, then fled from Park Mills before driving to his girlfriend's house in Bramley in a panic where his hair, skin and t-shirt began burning off.

Mr Roberts, of Winrose Avenue, Belle Isle, died in the burns unit at Pinderfields General Hospital 10 days later where he had 37 per cent burns.

A Leeds inquest heard that the voltage was so high the implement used to get at copper wires may have melted completely.

In a police statement read out in court, girlfriend Nina Hurley, of Bramley, told of the horrifying moment she heard Mr Roberts - also known as Bod - screaming in his van outside her home.

"At about 5.10am I heard Bod's van coming along the street. I heard this strange screaming noise. Bod unlocked the front door and screamed 'help me'. He came into the front room, sat in the chair and appeared to hyperventilate. He was shaking and his teeth were chattering. He was panicking.

"His skin was splitting on his hands and lips. His T'shirt had been burnt off. His face was all burnt, the only white was his eyes and teeth. His eye brows and eye lashes were all burnt."

The inquest heard there were prominent safety notices from Yorkshire Electricity warning of the high voltage and danger of death.

These were based around the transformer room within the mill on South Street where there was 11,000 volts buzzing about inside.

The court heard Mr Roberts' injuries were caused by contact with a switch box which would have had an impact similar to putting a "blow torch on the skin".

Police found that equipment had been tampered with and that copper had been systematically stripped.

A leather belt was found on the railings above a wall at the site - probably used by Roberts as he fled.

Assistant deputy coroner Melanie Williamson said: "I am in absolute amazement how Mr Roberts managed to leave the transformer room, climb over the wall and into the car and drive over to Nina Hurley's house."

Ms Hurley called 999 and he was taken to Pinderfields where he later died.

The inquest heard that Mr Roberts had gone to the mill two nights earlier with Jill Dowthwaite who he had been seeing for a month.

They broke off the padlocks and climbed over railed walls in a bid to steal scrap metal.

Through a police statement read out in court, Mrs Dowthwaite told how she could hear a loud buzzing noise.

The pair then left, only for Mr Roberts to return to the spot alone two nights later on August 4, 2007.

He died of multiple organ failure at 2.37am on August 14, 2007.

The coroner recorded a verdict of death by misadventure.