A couple found liable for an accident on a bouncy castle that left a boy brain-damaged have won their appeal against the ruling.
Sam Harris, now 13, of Spalding, Lincolnshire, suffered a broken skull after a 15-year-old boy kicked his head while performing a somersault on the castle in September 2005
Lawyers for Catherine Perry who, with her husband Timothy, was in charge of the party attraction, had told the Court of Appeal that her supervision was no different from that of "parents up and down the land".
They argued that High Court judge Mr Justice David Steel applied the wrong legal test to the conduct of Mrs Perry, who was supervising children using the castle, in relation to the conduct of reasonably careful parents in the same circumstances.
The judge ruled, in May, that the Perrys did not provide enough supervision after hiring the castle for their triplets' birthday party in Strood, Kent.
He found them liable for damages - estimated at more than £1 million - for Sam, who now needs round-the-clock care.
Today, Lord Chief Justice Lord Phillips, sitting with Lord Justice May and Lord Justice Wilson, said that Mrs Perry, who went to help another child on another inflatable during the seconds that the accident happened and had her back to the bouncy castle, could not be held at fault for the way that she acted.
"The manner in which she was supervising activities on the bouncy castle and the bungee run accorded with the demands of reasonable care for the children using them.
"The accident was a freak and tragic accident, It occurred without fault."
Sam was 11 when the much taller and heavier boy caught the left side of his head with a heel.
Bringing the case through his mother, Janet, of Long Lane, Gedney Hill, Spalding, Lincolnshire, he sued the Perrys of Jersey Road, Strood, Rochester, Kent.
Allowing the appeal by the Perrys, who were insured, Lord Phillips said that children played by themselves or with other children in a wide variety of circumstances.
"There is a dearth of case precedent that deals with the duty of care owed by parents to their own or other children when they are playing together.
"It is impossible to preclude all risk that, when playing together, children may injure themselves or each other, and minor injuries must be commonplace.
"It is quite impractical for parents to keep children under constant surveillance or even supervision and it would not be in the public interest for the law to impose a duty upon them to do so.
"Some circumstances or activities may, however, involve an unacceptable risk to children unless they are subject to supervision or even constant surveillance.
"Adults who expose children to such circumstances or activities are likely to be held responsible for ensuring that they are subject to such supervision or surveillance as they know, or ought to know, is necessary to restrict the risk to an acceptable level."