A man was burned alive at 280C when he climbed inside an industrial oven to clean it and became locked inside.
Alan Catterall, a father of three, had gone inside an oven designed for moulding plastic kayaks to clean molten plastic escaping from a mould at Pyranha Mouldings Ltd, in Runcorn, on 23 December 2010.
His colleague Mark Francis accidentally trapped Mr Catterall, 54, inside when he turned on the power on the machine, causing the doors to close shut and lock from the outside, the Liverpool Echo reports.
The court heard that Mr Francis was due to marry Mr Catterall's daughter.
Mr Catterall made desperate attempts to free himself with a crow bar but was found dead inside the oven over ten minutes later.
Prosecutor Andrew Thomas, QC, told Liverpool Crown Court: "Although Mr Francis does not seem to have appreciated it, the effect of turning the power back on was for the automatic doors to default to their closed position.”
The court heard that the locking bolt would drop into place when the doors closed in that way.
Mr Catterall was only found when two members of staff saw smoke emerging from the oven and opened the door, where Mr Catterall lay dead inside.
Mr Thomas said: "He had been in the oven for at least 10 minutes when it had been at or approaching its operating temperature (280 degrees Celsius)."
Prosecutors allege that the company, which manufactured their own ovens as opposed to buying them in, designed the doors to close automatically in order to save fuel.
They allege that was a breach of a fundamental engineering principle that turning the mains power on should not have automatically started the machine.
Mr Thomas told the court workers in the factory had created their own procedures for staying safe, such as asking a friend to guard the door or keeping open with a metal bar. He said a number of “near misses” lead to concerns over its safety.
Prosecutors allege that Pyranha failed to carry out sufficient risk assessments or provide written instructions on how to enter the oven safely.
Pyranha Mouldings Ltd is facing a charge of corporate manslaughter. The company’s managing director Graham Mackereth, 65, of Preston Brook, Runcorn, technical director Peter Mackereth, 60, of Llangollen, North Wales and self-employed electrical engineer Paul Keddie, 49, from Llangollen, who designed the oven's control system, all deny breaches of health and safety laws and all charges.
The trial continues.