A seven-year-old boy suffered a fatal shock in front of his parents caused by defective pub garden lights installed by an electrician with 50 years experience, a court heard.
Harvey Tyrrell collapsed in front of his mum and dad after sitting on the decorative lights, jurors were told.
The court heard he stretched his arms back and touched a metal railing that - because it was exposed to the weather - electrocuted him.
Police rushed to the King Harold pub in Harold Wood, near Romford, in the London Borough of Havering, following the tragic incident at around 5.20pm on September 11, 2018.
Harvey was found unresponsive and he was rushed to hospital, but sadly he died just over an hour later.
The light fixtures are said to have had powerful stolen electricity running through the rig without proper safety mechanisms, the court was told.
Technician Colin Naylor, 73, denies gross negligence manslaughter after a post-mortem found the cause of death was electrocution.
He also faces a separate charge of failing in his duty as an electrician by not installing or maintaining the electrics in a way that prevented and protected others from death or injury.
Jurors heard there were several points where water had fallen into the defects that only made the entire venue more dangerous.
Naylor, who worked at the pub with his brother-in-law David Bearman, is accused of "raising his eyebrows" at the state of the electrics before he proceeded to continue to install the outside lighting regardless three months before the tragedy.
Snaresbrook Crown Court heard that Bearman, the landlord of the King Harold, has already pleaded guilty to gross negligence manslaughter and stealing tens of thousands of pounds of electricity last year.
Duncan Penny QC, prosecuting, said: "In the garden of a public house in Romford where he was playing with a friend of his, Harvey Tyrrell, who at the time was a seven-year-old boy, was killed when he was electrocuted as a result of the unsafe installation of an electrical lighting circuit in that garden.
"Harvey had been taken to the King Harold that afternoon by his mum and dad.
"The prosecution's case is that, together with another man - who was the owner of the premises - this defendant, Colin Naylor, who was the electrician who installed that lighting circuit in the garden of the public house is responsible for the manslaughter of Harvey.
"The Crown's case is that the defendant was grossly negligent in the installation of that lighting circuit and in the discharge of his duty as an electrician working at those premises to ensure safety - familiar as he was with the state of the premises in question, having worked there as he had for an extended period during the spring and the summer of 2018."
The prosecutor said the electrical lighting circuit contained numerous significant faults and showed pictures and diagrams to jury that showed how easy it was for Harvey to "stretch his arms and touch the metal railing, and therefore completing the circuit."
He added: "When young Harvey both touched one of the garden lights, by sitting on it, and took hold of some nearby metal railings which were behind him it seems clear that electricity then flowed through Harvey's body, causing him fatal damage.
"He collapsed to the ground in front of another boy with whom he was playing and these events were watched by a number of adults in the area who went immediately to assist him."
The court heard that Naylor had done several electrical jobs on the pub in the Spring and Summer of 2018, and even he had cause for concern about Bearman's previous work, who had bought the property for £900,000 in 2010.
Mr Penny said: "There can be no doubt that when the Health and Safety Executive came to inspect Mr Bearman's premises in September 2018 in the aftermath of these events, overall the premises were very dangerous.
"The defendant told the police officers that as an electrician of 50 years experience when he had cause to look at one of the distribution boards, known as fuse boards, in the basement of the public house the state of it had caused him, as he put it, to 'raise his eyebrows'.
"He accepted that, when shown it by Mr Bearman, he had indeed thought that the fuse board area needed some attention but in due course he had decided having spoken to Mr Bearman that he did not 'want to get involved in that side of it'.
"The Crown suggests that it is against that background that the defendant's conduct in the installation of the garden lights should be judged.
"After proper inspection, the whole distribution board was not properly connected to earth and the earthing of electrical circuits is a key safety feature in all electrical circuits which are installed domestically."
The hearing was attended by Harvey's parents, Danielle Jones and Lewis Tyrrell, who were supported by specialist police officers.
Naylor, who wore a striped shirt, navy jumper, dark padded coat and a medical face mask in the dock, denies the charges.
The trial continues.