The family of a dad who suffered "catastrophic" brain damage in a plumbing tragedy which left a friend dead have today lost a multi-million pound compensation case.
The family of former teacher Adeniyi Ayannuga took legal action against the makers of a household drain unblocker after he was overcome by hydrogen sulphide - a toxic gas which can be lethal with only one breath.
Mr Ayannuga had tried to help plumber pal Tito Gbadegeshin, who sadly died after collapsing trying to fix a sink.
He was left "catastrophically brain damaged" after Mr Gbadegeshin attempted to unblock his kitchen sink at his home in Peckham, south London, using One Shot Instant Drain Cleaner.
Mr Ayannuga also collapsed when the poisonous gas rose up from his kitchen sink during the ordeal.
He has been left so badly brain damaged that he is now in a "persistent vegetative state" and remains in a hospital for extremely disabled people, seven years later.
Mr Ayannuga's wife, Oluyomi Ayannuga, blamed the makers of One Shot, a sulfuric acid-based drain unblocker, and is claiming millions in compensation for her 58-year-old husband, herself and her family.
She claimed the One Shot must have reacted with another chemical product which had already been in the blocked drain to create the lethal gas.
But today, a senior judge threw out her claim after finding that the gas which poisoned Mr Ayannuga and killed Mr Gbadegeshin must have risen up into the kitchen from the sewers in what was a "tragic accident".
"My conclusion is that what happened was a tragic and unforeseeable accident and that the use of the One Shot that evening was coincidental," said Mrs Justice Yip in her judgement at the High Court today.
Opening the case during a trial of the claim last month, the family's barrister Simeon Maskrey QC told the court of the "traumatic" circumstances of the case.
Mr Gbadegeshin, 54, had gone to the block to unblock the sink of the Ayannuga family's flat on New Year's Day, 2015, he said.
While there, he poured some One Shot Instant Drain Cleaner into the sink and left the kitchen to allow the acid to begin its work.
He returned to the kitchen, but the family ran to his aid after hearing him collapse to the ground.
Mr Ayannuga, who had worked for South West Trains, and his wife were also both overcome by the toxic gas.
Mr Gbadegeshin died and, although the Ayannugas survived, Mr Ayannuga was left catastrophically brain damaged.
Mr Maskrey claimed that the drain unblocker must have reacted with lime sulphur in the sink, producing the gas.
But lawyers for product maker, One Shot Products Ltd, said that was "implausible" and that it was more likely that sewer gas had risen into the flat.
Ruling today, Mrs Justice Yip said there was no evidence of the Ayannugas having had lime sulphur-containing products in their flat.
Lime sulphur is usually seen in products used to treat pet parasite infestations and in some hair care products.
Previously reported cases of hydrogen sulphide poisoning in homes had been linked to gases released when people try to unblock sinks, she continued.
That meant it was Mr Gbadegeshin's removal of part of the pipework under the sink that had more probably allowed the gas to enter the kitchen.
"I conclude that the claimants' case that lime sulphide had been poured down the sink after it became blocked is implausible," she said.
"On the other hand, the defendant's theory that sewer gas escaped from the waste system when Mr Gbadegeshin removed the pipe is scientifically sound and is consistent with what is thought to have occurred in other tragic and rare instances.
"It required the existence of particular conditions at just the moment the pipe was opened. That such conditions existed was incredibly unlucky and was not something that would usually occur.
"In all the circumstances, I find as a fact that the hydrogen sulphide was not produced as a result of the use of One Shot. Rather it resulted from an escape of sewer gas when the pipe was removed.
"The use of One Shot was therefore coincidental and did not make a material contribution to the death of Mr Gbadegeshin or the injuries sustained by any of the claimants."
She continued: "In simple terms, the claimants' pleaded case on defect has failed because they have not established that the product did in fact produce the toxic fumes."
She added: "As I indicated at the start of the trial, the Ayannuga family have my utmost sympathy.
"I extend that sympathy also to those who mourn the loss of Mr Gbadegeshin.
"I know the trial was not easy for Mrs Ayannuga and the outcome will be bitterly disappointing.
"My conclusion is that what happened was a tragic and unforeseeable accident and that the use of the One Shot that evening was coincidental."
She dismissed Mrs Ayannuga's claim.