A schoolboy died when the toxic fumes produced by a petrol pump designed to keep his family home from flooding poisoned him in his sleep, a coroner has ruled.
Seven-year-old Zane Gbangbola died on February 7 2014 after the outside of his home near the Thames was engulfed in flood water.
His parents believed the water was contaminated with toxic hydrogen cyanide from a nearby lake built on a former landfill site.
But Woking Coroner's Court heard evidence that the boy's parents hired a petrol pump to clear the flood water in their basement, which was used for up to six hours on the day the boy died and pumped deadly fumes into Zane's upstairs bedroom while he slept.
He was discovered unconscious at around 3.30am the following day by his mother, Nicole Lawler, and pronounced dead an hour later in hospital.
Ms Lawler and Zane's father Kye Gbangbola, of Thameside in Chertsey, Surrey, have spent the last two-and-a-half years campaigning for further investigation after disputing post-mortem examination results that said Zane's death was because of carbon monoxide poisoning.
The couple gripped each other's hands at various stages of the inquest findings, read by senior Surrey coroner Richard Travers during a two-and-a-half-hour hearing on Wednesday.
But Zane's mother - and later Mr Gbangbola - left the courtroom as Mr Travers disputed evidence from the family that the pump had only been left on for "a few minutes".
Mr Travers concluded: "I find the cause of death was carbon monoxide toxicity, from fumes generated by a petrol pump used by his family to clear the house of flood water."
Mr Gbangbola had been working in another bedroom upstairs from 7pm the day his son died, around the same time the "popular and generous" schoolboy and church-goer went to bed. The father was found slumped on his bed in a half-seated position when paramedics were called to the scene.
He was paralysed and wheelchair-bound as a result of the incident, while his wife - believed to have been "snoozing" that evening - made a full recovery.
The court heard Ms Lawler only rented the Honda petrol trash pump from Surrey Hire Services the day before Zane died.
But the couple's testimony in court that the pump was only "tested" for a few minutes and that it was switched off before lunchtime was rejected by the coroner - they had previously said it had been used until the early evening, the court heard.
Mr Travers said: "I have no hesitation that Ms Lawler and Mr Gbangbola did not want the pump to be working when Zane went to bed.
"But I cannot accept their accounts that on February 7 it (the pump) was used for no more than 20 minutes and not after lunchtime."
Expressing his sympathy to the family and their supporters, many of who were wearing red flowers as a symbol of solidarity in the packed courtroom, he added: "I must decide dispassionately where the truth lies.
"Though most evidence was reliable and accurate, I found they provided an accurate original statement (that the pump had been used until 6.30pm) but not to me at this inquest.
"I find it was used for six hours and stopped at 6.30pm, presumably when it ran out of fuel."
Surrey Police said no criminal charges would be brought over the boy's death.